Not to turn this into all-Calacanis all the time (he's not a bad guy, just annoying and a fun target) but, here's some collected Jason C wisdom on web 2.0:
Youtube.com = not a real business
Digg = extremely raw and suspect
Wikipedia = on the verge of coming apart
critical bloggers = freaks
The first three on the list have the distinct disadvantage of having either having more users/reach or being rumored to sell for more then Weblogsinc. The last item is true.