YouTube and the Largest Google Website Optimizer Test in History
In January of 2009, YouTube approached VKI Studios to develop a test using Google’s own Website Optimizer. Working together, VKI Studios and YouTube implemented one of the largest Google Website Optimizer (GWO) experiments in history, with a whopping 1024 combinations and more traffic than any reasonable site should have to maintain. The results: a 15.6% increase in YouTube sign-ups.
Emphasis mine. Great interview. Even if Google Website Optimizer doesn’t exist in this state any longer, the article shows the tremendous potential of asynchronous user testing.