What decides either-or is simply revenue (or monetization as some call it): There’s still a lot of innovation and older (relatively speaking) companies are replaced by newer, as older services and applications become unpopular. Hence, I’m sure we will see many more “About.me”s, “LinkedIn”s, “Twitter”s, “Facebook”s etc before investor money and patience runs out.
Remember that after the last IT boom there were hardly any companies left, yet the ones that remained had grown very big and über-profitable. The rest went bankrupt or were acquired, and also many smaller investors went bankrupt. That will also happen this time around.
The leading companies in social and Web 2.0 are acquiring companies like crazy. That’s a sign the opportunities are decreasing, but congrats to all smaller companies that get acquired before that happens.
There are simply too many that are called and too few that can be fed if we talk 2012 and forward.