It looks like I could be a rational egotist and still vote for a left leaning party that wants to increase taxes on high incomes within a capitalist system. After all, it's about my individual preference. Do you agree?
No. It's not merely about individual preferences--it's about individual preferences AND individual rights. Your preferences no longer matter once they extend beyond your property or interfere with someone else's rights.
Is there a principle or some type of heuristic specific to Objectivism that you find relevant or inspiring, regarding reason and logic?
Well, there's my sig.

After that, there are the Wizard's Rules from the Sword of Truth series (written by an Objectivist, though he wasn't when he wrote the first few). But for the most part I don't really look for inspiring heuristics or the like in philosophy; I look toward philosophy for explanation, not inspiration. For inspiration, I look to art.
ThunderChunky said:
1) Can you explain why selling snake oil is or is not ethical?
It's not, if you know it doesn't actually work. It dishonestly presents the product as something it's not; there's no way for that to be moral. Note that this is different from UNknowingly selling something as something. What I mean is, folks who sold asbestos insulation before we knew what it could do to lungs weren't guilty of fraud; they acted on the data available, which is all we can ever do.
2) How about exploiting addicts?
Immoral, but not necessarily illegal. It's pandering to the worst aspects of a person, and feeding off their destruction--inherently vicious. I will say that this concerns the PRACTICE, not the PRODUCT. One can sell tabacco perfectly morally--sure, it's dangerous, but there's nothing wrong with sharing a cigar at the birth of a child, or the return of a combat veteran.
3) How does objectivism deal with tragedy of the commons situations?
Simple: we eliminate the commons. For areas where this is not possible (say, the atmosphere) we would rely on the courts to determine if someone has violated our rights. For example, someone living downwind of a factory that discharges toxic materials into the groundwater would have a moral and legal obligation to clean those discharges up, and pay any damagess involved. Same with air polution.
4) Does Objectivism require free will?
Yes. Objectivism includes ethics, which requires choice.
If so, how does it deal with the inconsistency of free will and modern science?
I've yet to see science address this question, so my impression is that the question starts with a false premise.
Tommy Jeppesen said:
Rand did a "bad" job of understanding how ethical values come about in reality, because she overlooked the effect of biological evolution.
Not in my opinion. The statement "There are no individuals in evolution as individuals..." is, in my professional opinion, a complete misunderstanding of evolution. Evolution is an emergent property of populations, but selection acts upon individuals. Rand's ethics logically follow from that.
Pixel42 said:
Also: what happens when rights conflict?
I would have to see an example to understand what you're talking about.
Person A's right to freedom of speech may conflict with person B's right not to live in fear.
There isn't a "right not to live in fear". There IS a right to life and liberty, and threats against those are therefore not allowed. However, if Person B believes that Person A issued a credible threat, Person B can take Person A to court, or arbitration, or the like.
Person A's right to burn fossil fuel to enhance their lifestyle may conflict with person B's right to farm their land without it disappearing beneath the waves.
Again, these rights are mere fabricataions. That said, again, Person B could take Person A to court over their losses.
Person A's right to maximise their wealth may conflict with person B's right to a fair wage.
There is no right to a fair wage, or to maximise one's wealth. There is a right to property and free association, however. Person A can do whatever they wish with their property, including employ others to work for them. Person B can choose to work under the terms offered by Person A, to attempt to re-negotiate their salary, or to work somewhere else. And please don't fabricate purely fictional situations where one company owns ALL the businesses in an area; the only times this happens are when companies are allowed to issue scrip in place of actualy payment, and I believe scrip is an anti-concept (a concept that is both logically indefensible and designed to destroy some valid concept, in this case "employment"). I see no way, without massive special pleeding, for there to be only one employer in the area and no potential to even try to make your own business.
Secondly, rights are related to actions, not inanimate mater. They are things you can do. One can
own things, or
persue ownership of things, but one has no right to any thing outside their own body. What I mean is, once you have something you have the absolute right to keep it, or use it as you see fit (provided it doesn't violate the rights of others); however, there is not a single thing in the universe outside of your own body that you have an inherent right to. One obtains property by traid, or by work--either you exchange something you own for something someone else owns, or you go out and get it from the wilderness, or you grow it. If a right to a wage was real, every human on Earth would be getting a wage--regardless of whether they work or not. The only way to enact such a program is to take money from those who have it, which is a violation of their property rights (they can give the money away as they see fit, but no one has the right to take it). Wages don't grow on trees, and they aren't mined--one must trade for them. And there's no right--there cannot be a right--to someone else's property.
This is what I mean by lookign at things from the other perspective. A right to a living wage is a perfectly sound right under a socialist ethical theory; however, you cannot take a socialist ethical theory and ask an Objectivist to defend it. It's akin to demanding a Christian defend an atheistic interpretation of the clergy; the premise contradicts the question.
Is there any, seemingly reasonable, right which doesn't potentially conflict with another equally reasonable one?
Depends on what you consider reasonable. Many of the "rights" you listed are not rights according to the Objectivist definition. A "right to a fair wage" isn't a right under any rational definition, in my opinion. If you ask whether ther are rights under the Objectivist use of the term that conflict with other rights, the answer is no. Interactions may be complex, but they are not conflicting. Rand pointed out that this is why property rights are so important--property rights are necessary to determine who's got the final say in a situation. If I own a company, I get final say in how much my workers get paid (I may deligate this to others, such as VPs or managers, but it's still my authority). If a worker doesn't like it, they have the right to leave--I cannot enslave them--but they DO NOT have a right to my money. That's why it's my money. Property rights can be used similarly: if something you do impacts my property (not my property VALUE; loss on an investment is the risk one takes fo rmaking an investment), you either have to gain my consent or you have violated my rights.
Squeegee Beckenheim said:
If all force is verboten under and and all circumstances, then how could the police arrest someone who doesn't want to be arrested?
The highlighted premise is wrong. The initiation of force is forbidden. Self-defense is manditory. And the police operate via the population deligating their right to self-defense under specific conditions (we retain it when we must defend ourselves violently in order to survive, for example). Nothing in Objectivism suggests pacifism, and I'm of the opinion that pacifism, like anarchism, cannot actually exist in the real world.
Sorry if I misseed anything important. Like I said, I'm doing this on my lunch hour. Hopefully I didn't mangle anything too much! And I'm gong to have to think more on the issue of rights conflicting.
Also, to clarify the quesiton of what Objectivism means to me: If someone says they are an Objectivist, you can assume they agree with what Rand said. The burden is on them to demonstrate that they do not accept something. For example, I disagree with Rand's views on sexuality--but it's perfectly reasonable for someone to assume I don't until they hear otherwise. I've also said that I agree with most of what Dr. Hsieh said (her blog/podcast is "Noodlefood" if you're interested), and the same assumption can be made there.
That said, I limit this to Rand. It is not reasonable to assume I agree with what Piekoff said, or what Greg Biddle says, or the like. (An exception is "Ominous Parallels", a book which Rand endoursed, but if you know that much it's safe to assume you know enough that this statement is unnecessary.) There are a lot of stupid people that use Objectivism to mask behaviors that directly contradict Objectivism, and it's those people that I don't have any interest in defending.