Forums and platforms for crowdsourcing

I've always thought of crowdsourcing as a narrow, niche thing. But then I ran across this excellent list of forums and platforms for crowdsourcing. Skimming down the list, I realized that crowdsourcing is actually starting to play an important role in quite a few industries.

It looks like we're just starting to climb the adoption curve here. Where should we expect crowdsourcing to stop? What sorts of problems will it solve (and not solve)? Who won't ever use it?

PS: In case you haven't run across the term before, here's wikipedia's definition of crowdsourcing:

Crowdsourcing is the act of outsourcing tasks, traditionally performed by an employee or contractor, to an undefined, large group of people or community (a crowd), through an open call.