There is, Bitbucket was exclusively Hg before Bitbucket saw Git's popularity. This is my opinion: Bitbucket is like the new Sourceforge. I'd be interested to see a survey on Hg and Git usage today.
IIRC from when I looked ~2 years ago, > 80% of new repositories on bitbucket were using git. (and that's a conservative estimate, because I'm not entirely sure whether it clearly was over 90% or not, but it might (likely) have been).