The GitLab number tallies with Emily's answer, which gives me some moderate confidence that these numbers are in the right neighborhood. I'm also going to assume that the users-vs-teams numbers are all in roughly the same proportion.
Based one these numbers it doesn't make much sense to target BitBucket unless either 1) they're growing much faster than GitHub (unlikely) or 2) their customers are a much better fit for Reviewable (possible, but it would have to be a truly significant difference in userbase composition). Targeting GitLab doesn't appear to make sense at all (as a business), though perhaps they're growing fast.
GitHub: 31M users
BitBucket: 6M users, 1M orgs
GitLab: 100K orgs
The GitLab number tallies with Emily's answer, which gives me some moderate confidence that these numbers are in the right neighborhood. I'm also going to assume that the users-vs-teams numbers are all in roughly the same proportion.
Based one these numbers it doesn't make much sense to target BitBucket unless either 1) they're growing much faster than GitHub (unlikely) or 2) their customers are a much better fit for Reviewable (possible, but it would have to be a truly significant difference in userbase composition). Targeting GitLab doesn't appear to make sense at all (as a business), though perhaps they're growing fast.