A/B testing in the wild

You always hear about people doing A/B testing "out in the wild" (as well as examples of how it can be misused) but it's rare that it is ever noticeable (which is kind of the point). So when my colleague Aaron and I were working next to each other and happened to visit Salesforce.com at the same time, we were surprised to see the following: sf-a-b-no-trial and this... sf-a-b-trial1 Notice the difference? Someone at Salesforce is testing out whether people will sign up for the free trial (top menu, red button). Does anyone have any other examples of A/B testing you've come across out in the wild? Would love to see examples.