I might be very wrong, but... Dunno, I sometimes used to search for an specific model, and only remembered the name or part of it (a partial chain works too, like in Google). It might not be one of your regulars, and never have paid you tokens, but he might be a potential customer, those tokens would be lost. One uses the search for this. Change your name and you might loose quite some tokens (at least, following this logic, and knowing the little I know about it). Of course, it all can happen. You get to set such a great name, and also have some luck, and your new nick brings you fame and fortune. But I would not bet on that, personally.
I don't have the experience others have here, this only is what tells me common sense right now, and maybe also my average experience working in SEO stuff for companies. In this kind of thing... I would say it might hurt your promotion if you have been camming sometime, probably. I would need *a lot* of info, to know well. IE, how internally the servers of myfreecams are handled, for example. What SEM/SEO techniques do they use. If they are banned or blacklisted in several sites for backlinks. A large etc. (and more knowledge, as I know just a bit more than the average Joe about this) . But in my view... You have an important page in the case of MFC. The profile page. It's sth like profiles.myfreecams.... /your_nick_name.
I... might be wrong, but that, being a full url, might have got quite some clicks, visits, and it might have certain weight in google (not rank, as this would be a case of a full domain), in many cases, specially those being around more than very few months. You might loose all those SEO benefits, like whenever you change an URL. And no way to make 301 redirections here, you don't control their servers...
Basically I mean: Not only you loose the potential members searching internally for you, using built-in MFC search system (quite good and fast, btw). You might be also destroying quite some Google related "points", and so, traffic to those profile pages. I'm betting... not only for people doing just random searches using terms like cam, sex, or any other content showing up in your profile pages (indeed, maybe some discover MFC due to your profile pages!) , but also, users lazy enough, or not realizing there's a search feature in MFC, will just google the model name, lol... And tried, it pops up first result, no probs, unless is sth like "Sasha Gre" or something... Then would be buried, surely, under several result pages.
Excuse me is I'm way off the reality here. I don't know MFC internals or the like... Just speaking generally about a site and case like this...