The issue here isn't the legality of the SEC filings, necessarily. The issue lies in the fact that, subsequent to Romney's "departure" from Bain in 1999 (I put "departure" in quotes to indicate the potential that he was, at least on paper, still part of the company in all likelihood) the company, which he still had a controlling interest in, was responsible for the dissolution of many American jobs. As others have said, the fact that Romney may or may not have delegated the responsibility for the day-to-day operations of Bain to others in the subsequent three years after his ostensible departure from Bain in 1999 is immaterial to the fact that, if he is listed as the controlling interest during those three years, then he is ultimately responsible for everything that company did during those three years. Bain was directly responsible for the loss of something like 100,000 American jobs during that time period IIRC; therefore, by extension, Romney bears some responsibility as well, and it speaks directly to the claim that he has been constantly making that he knows how to create jobs IN AMERICA.
It is entirely likely that Romney did delegate his power over day-to-day operations at Bain, but that does not by any definition of the word abrogate his own responsibility for the actions of those he delegated the power to. I delegate jobs all the time in the military, but I'm still ultimately responsible for ensuring that those jobs are completed, even if that just means I get my soldiers to report in when a job is completed. Romney is just as responsible as I am for the actions of the people below him.
The whole point of this issue is that Romney has been touting his ability to create jobs since practically the beginning of the primaries and througout the election cycle; this issue seems to reflect directly (and badly) on that claim, since Bain in fact caused jobs to be LOST during those three years. It also speaks directly to his claim that a businessman is the right person to run a country, which is an ENTIRELY different animal from a corporation when one examines the day-to-day operations. I've worked in the government in various capacities (as a government consultant and in the military) for my entire adult life; trust me, I know the difference between a government and a corporation, and they are VASTLY different in terms of operations. Being a government consultant has given me a unique look into the differences between the government and a corporation, since my day-to-day work was conducted in the government and was conducted according to their standards, but I still had numerous obligations to the corporation I ultimately worked for that were entirely different from the equivalent requirements in the government. Ultimately, I find Romney's claim that a businessman can run the government to be specious at best, and with the revelation that he still ostensibly held a controlling interest in a company that LOST American jobs for quite a while after he stated he left, I find myself losing confidence rapidly in the notion (which was already remote to begin with) that he could possibly run the country better than President Obama has in the past four years.
My two cents American; take them or leave them, as you wish.