I can't believe you folk are still carrying on this thread. Time to re-enter to address some of the BS being sprouted.
CynicalSkeptic - your math is fine, unfortunately what you're talking about is a pyramid scheme and not legitimate MLMs. It doesn't matter how good your math is if your assumptions are wrong, and yours are wrong for a number of reasons, but I'll take the simplest for now.
I have people in my downline who have ZERO downline, and they profit. One of the simplest defining marks between legitimate MLM and illegal pyramids is the answer to a theoretical question "can the last person who joins profit?"
If the answer is No, as you are claiming, then it isn't an MLM, it's an illegal pyramid.
So, by definition, what you are talking about is NOT an MLM.
Having said that, there are many companies that call themselves MLM that are not, they are illegal pyramids. One problem may be that you're believing them when they say they are MLM, and attributing the characteristics of illegal pyramids to MLM.
Just because someone says they're an MLM doesn't mean they are.
I'd suggest another core problem is that you believe recruiting is the raison d'etre of companies that use MLMs. It's not. In legitimate companies, "mutli-level marketing" is simply a marketing strategy for increasing product sales, and thus revenue. It is not a necessity for achieving revenue. Contrast that with BurnLounge, I believe the most recent company taken to court by the FTC as being a pyramid. To profit in BurnLounge you have to recruit people - the money comes from fees paid by new recruits for their websites. The margins on the actual products (downloadable music) is way to small to be able to cover the expenses of generating the sales. The only way for BurnLounge to make money as a company, and the only way for it's reps to make money, is to recruit new reps. It's a classic pyramid scheme using an ostensibly real product as a cover. That's why when the court brings down it's decision in the next month or so, it will declare them a pyramid scheme. It's the same reason YTB Travel got declared a pyramid scheme by California courts.
By contrast, Amway reps get no revenue at all by simply recruiting and Amway itself merely covers costs with it's membership fee - where it even has one (in some countries it doesn't have one). Virtuall all of it's revenues, and all of the revenues of it's agents, are based on product sales, not recruiting.
You're right in saying that "MLMs can not work for everyone", but that applies to every business. It's not possible for everyone to make money selling Amway. It's not possible for everyone to make money selling computers. It's not possible for everyone to make money selling apples. If everyone tried, who would buy?
On the other hand, if there was a chain of a hundred computer stores all trying to profit - can all of them make money? Sure, there's still plenty of potential customers. If there's a network of a hundred amway distributors, can all of them make money? Sure, there's still plenty of potential customers.