From The Economist:

Projects that fail to cope with open source's vulnerabilities usually fall by the wayside. Indeed, almost all of them meet this end. Of the roughly 130,000 open-source projects on SourceForge.net, an online hub for open-source software projects, only a few hundred are active, and fewer still will ever lead to a useful product. The most important thing holding back the open-source model, apparently, is itself.

-- Open, but not as usual, 16 March 2006.

In a recent email newsletter, Sourceforge admins said that clearing up dead projects was a much-requested feature, and that they would be working on doing so.