Gizmodo has a great essay on how Yahoo killed Flickr. I think this excerpt is a pretty good summary:
It was a stunning failure in vision, and more or less the same thing happened at Flickr. All Yahoo cared about was the database its users had built and tagged. It didn’t care about the community that had created it or (more importantly) continuing to grow that community by introducing new features.
It’s worth a read. It’s a textbook example of how not to build/manage a product. Yahoo isn’t in it’s current situation by accident or chance. The upside is there’s a bunch of good lessons for everyone inside and outside of Yahoo here.
Love or hate what Facebook is doing, they are essentially the antithesis. Every decision Facebook makes is seemingly about growing the community and features that increase engagement. There are of course many other ways to fail.
The Internet is a network/community of cooperation. If you forget about the network/community factor, you’ve lost.