I think it's one of the earlier examples of why "grow userbase now, figure out how to monetize it later" can be a bad idea. There was a time when (perhaps) a majority of open source projects were hosted on sourceforge, and I think they assumed that that would just translate to profit (or sustainability) eventually. When that didn't happen, and then they had to compete with Google Code, it began the slide down the slippery slope to the spam-infested site that it is today.
I hope that's changing. We need more options for hosting software projects, we can't rely on github being benevolent forever.