Great data from BuiltWith (as usual), but a few key questions remain unanswered:

1) how much usage are the sites measured getting out of the A/B testing solutions they're using? I rather suspect that there are order of magnitude differences in tool usage that this measurement doesn't capture.

2) IMO it's really the usage among the top 2-5K sites that matters, and even within that it's the top few hundred that drive 80%+ of ecommerce. What tools they're using are a very, very important measure of share of A/B testing budgets being spent.