you might like this quote from horowitz of yahoo in newsweek on why they bought flickr.

Flickr was a good business, too, as many users chose to pay the $25-a-year fee for unlimited photo storage and relief from advertising on the site. But that’s not why Yahoo bought it for an estimated $35 million. “With less than 10 people on the payroll, they had millions of users generating content, millions of users organizing that content for them, tens of thousands of users distributing that across the Internet, and thousands of people not on the payroll actually building the thing,” says Yahoo exec Bradley Horowitz. “That’s a neat trick. If we could do that same thing with Yahoo, and take our half-billion user base and achieve the same kind of effect, we knew we were on to something.” see source