httpwebwitch - 8:18 pm on Dec 2, 2010 (gmt 0)
Note that this hack can't return your entire browsing history. What it can do is tell whether a particular URL is in your browser's history.
You can glean quite a lot of insight from just a few "hits" if you query the history creatively. It depends what you want to find out about your visitors.
Once that information is received at the server, your web experience can be tailored to your browsing habits.
Tracking clicks makes sense; why would someone not do that. Tracking mouseovers... not as much. I don't consider tracking mouse events to be privacy violations, though it is a bit creepy.