Paul Scrivens has made a list of the Top 10 Web 2.0 Losers. It includes Odeo, Squidoo, Edgeio, Flock, Netscape, Microsoft, AOL, Bloglines, SixApart, and Technorati. I'd also put Riya into the list, but that hasn't been fully proven yet.

One thing about these companies is that they all have great technology that is extremely useful to one group or another. The reason they're 'losers', however, is that while their technology may have an audience, they're not the 10+ million user technologies that allow you to pay back $10+ million investments. If more of them had started small, they might have a great niche, but with massive amounts of money floating above their heads, they're going to struggle to break even.