[Fomite]

While we're on the topic, Bayesianwitch.com's description:

"Your new homepage goes viral, but you aren't sure what copy is converting. Hook that copy up to BayesianWitch and only converting copy will be showing. No waiting days for the answers from an A/B test."

Seems to imply a reliance on "correlational" data. Is there some hidden randomization in there? Or are you giving your clients a lower standard of evidence?

[yummyfajitas]

We are using a lower standard of evidence than medical decisions. The goal is to get as many clicks/conversions as possible in aggregate, most of the time. I.e., if you have a call to action ("3 day sale", "spring sale", "march sale") that dies in 3 days, we'll do the best we can to increase your conversions in those 3 days.

Similarly, if you have 10,000 seo-optimized microsites, each with traffic too low for a per-site A/B test, we'll improve your conversion rate across the 10,000 microsites.

If you want to make a long term change (e.g., logo, button color, feature) for a high traffic site (your one and only landing page) you are better off using a traditional A/B test.