Facebook sucks in a lot of ways. I'm not a fan, in fact I'd actually quite enjoy seeing Zuckerberg crushed. There is just very little else online that facilitates shared experience.
Myspace has zero interest or ability to push itself further. Google hasn't really thrown its full weight behind orkut, not least because they have a much better money maker they need to protect. So the next generation facebook killer will probably have to be a startup - which means they have to be significantly better to attract users and reach a critical mass.
Orkut is quite possibly the worst name for a social network that I've heard. I have no idea why it was chosen, or what significance it has, but it's definitely not an advantage. Nobody I know would hear Orkut for the first time and think either "Social Network" or "Google." (In contrast to, say, "gmail," which immediately evokes email and google).
Myspace has zero interest or ability to push itself further. Google hasn't really thrown its full weight behind orkut, not least because they have a much better money maker they need to protect. So the next generation facebook killer will probably have to be a startup - which means they have to be significantly better to attract users and reach a critical mass.