The big announcement was fine. The problem is they hardly let anyone in after the big announcement. I remember there being a huge hype for Google+ when it was announced. But almost no one got invites, and those that did couldn't do anything on it so they quickly lost interest. It's hard to get excited about a social network when none of your friends can be a part of it.
Yeah, in hindsight Facebook looks especially clever in terms of how they managed their initial roll-out. Going university by university meant that they got to gradually ramp things up infrastructure-wise, and created the I-want-it-because-I-can't-have-it effect that I think a lot of companies go for with phased roll-outs, invitations, etc., but because any given school would get it all at once, as soon as your school got it, most of your peer group would also get it at the same time, which avoided the chicken-and-egg problem Google+ experienced.
