An Anthropology of Google’s Search Experiments (with all data exposed, of course).
Never will happen, but we get some tantalizing hints in this post on the Google blog:
At any given time, we run anywhere from 50 to 200 experiments on Google sites all over the world. I’ll start by describing experimental changes so small that you can barely tell the difference after staring at the page, and end with a couple of much more visually obvious experiments that we have run. There are a lot of people dedicated to detecting everything Google changes – and occasionally, things imagined that we did not do! – and they do latch on to a lot of our more prominent experiments. But the experiments with smaller changes are almost never noticed.