There is a way to get profitable, companies like Twitter, Digg and Facebook haven't figured it out, yet, and it gives the whole web 2.0 business a bad rap.
MySpace is quite profitable to the tune of pushing $1 Billion in 2008: http://bit.ly/PJPc2
Dogster has been doing quite well in the advertising space: http://bit.ly/7WZL and http://bit.ly/ytNf They've been able to be profitable by hiring their own advertising sales team. They are getting CPM's of $20-40 for their email newsletter: http://bit.ly/p9nB
CuteOverload.com is profitable. icanhascheezburger.com is profitable.
Part of the problem with web 2.0 companies, is that a lot of them don't realize that they are media companies. Mainstream media companies figured out the monetization bit years ago. They make money by selling the content (Movies, Music, print media), selling advertising space on the content (TV, print media), or by branding and merchandising themselves (Star Wars, Saturday Morning Cartoons). * See Footnote
Mainstream media has also learned a long time ago, that you can charge a premium for delivering a targeted demographic. If you were able to launch a Social News site devoted to the people interested in buying car insurance, or people intersted in investing in day-trading stocks, your CPMs would sky rocket.
Dogster is making money because they figured out the setting up their own ad network and selling ad space on it was much better than using Adsense. TV stations, radio stations all have their own sales teams that sell ads on their networks.
* Newspapers and Print media are really struggling because their overhead is so high, and can no longer compete with online media. But, for years, these companies have been cash cows. Just look at how Rupert Murdock made his money.