I think I read somewhere (I definitely read this somewhere on a hackernews article) that facebook stores the text you type into your text box while using facebook even if you don't send it, i.e. if you retract the information and write something different, etc.
While facebook doesn't appear to have any business tracking this information, Google of course does, at least in the short run, with its auto-suggestion/auto-complete features, which of course use ajax and its backend servers to crunch the statistics on what it thinks you're going to say. Anyway, does anybody know if Google keeps this information? It feels like a violation of privacy in my opinion, and would be good information for anyone to know about.
Definitely am interested in knowing all major web applications that store this information in the long run. 'Gives a good profile on a company's overall eagerness (or perhaps desperation) to capture as much information about their users as possible.
EDIT: Thinking about this, I suppose I could monitor XHR requests via my Firefox Developer Console to track this behavior, but I wouldn't know what the server was doing with the information, and it would of course have to be encrypted so that's not a good way to see what's even going out. Maybe a Google employee could come forward about this.