I've actually found bitbucket slowly becoming a good competitor to github.

From a sales point of view, bitbucket's offering of 5 free private repos might actually help them attract more developers who are making proprietary apps and making money, and then more willing to pay for more repos in the future. I personally have quite a few repos there partly because I don't want the publicity of github (and partly because hg was quicker to learn than git :P). I also know a friend who switched to bitbucket simply due to the private repo offerings.

For open source though, github is probably the way to go.

This is all just anecdotal though, I'd love to hear some solid evidence if anyone has some.