It's not that people are making a big deal of it, it's people wondering if this might civilize internet discourse a bit. Probably not.

For now they have the choice. Will they still have the choice in the future? Who knows? The most popular sites are moving more and more towards using real profiles.

I think the main argument usually is that it may become more and more normal and then become forced. And no anonymity on such a big site would be lame, I'll give em that. I mean, there are search engines that can find pretty much anything tied to a phrase or name. People therefore don't like the idea of having a company snooking around their YouTube comments, say after a job interview or businesses keeping track of YouTube browsing history. Or having it used against you in legal matters, business matters, social matters or ratchet and clank: size matters in general.

So, yeah. Besides it allows you to be anonymous in debate, if you want to postulate ideas with being connected to them beyond your username.

...That's one argument anyway.