@Ted Clayton - I don't see any caveats here. They wanted to promote their new service, yes, but considering being blacklisted as a marketing strategy is too much for me. I've also launched online beta/demo programs and the last think you want is your web site down.

About Google, the methodology of 'shoot first, then ask' that is used when putting a website in a blacklist is, in my opinion, too severe. I'm sure they have the tools and technology to check false positives more accurately, specially when, as it seems in this case, the site wp-abtesting.com was safe according to Google Webmaster Tools.

About Theme Forest, Michael Ginsburg in a previous comment also mentioned that the problem he found was with ShapingRain, which is a theme provider that sells in Theme Forest. As far as I know, they only sell the Just Landed theme for WordPress. Following the comments (and also the content) in WP-AB Testing explanatory blog post you can also see that explicitly mentioned. It wasn't hard to find for me.

I don't see the point about second interpretations of what here happened. Maybe I'm too naive but, you know, I was never a follower of conspiracy theories. To me, Neil Armstrong walked on the moon, and Mr. Cabot's web just went blacklisted by mistake in a promotion day. It seems to be solved now. End of story.