I just happened to land on the github recent repositories page, and noticed a ton of spam:
A bunch of different users and projects advertising movie downloads. There's no project content, of course, just a "homepage" that points to a target url...
At first I was thinking, wow, these are some crazy spammers -- using git as a tool for spam! But on closer look, it seems like they're just hitting the website automating account signup and new repository actions.
Still, spam on github? Crazy! I guess no website is safe these days. If you're hosting user generated content, you need to think about detecting and blocking spam and automation of user activity.