I have read an article about sites like google and facebook using a redirect script to keep track of who clicks what links on the web. And since they have a lot of traffic, they are monitoring a lot users that are clicking a lot of links. However, they aren't the source of 100% of the links in the world, and thus they can not monitor every link that every user clicks on.
However, we (the smaller websites) are also capable of monitoring what our visitors click on, though we have to do it on a much smaller scale (we don't have as many visitors as facebook and/or google). The only problem is, we don't collect enough data for it to be very useful to anyone but us. However, if someone were to pay owners of the small sites for their click data, and combine it into one big dataset, it could be very useful. In fact, it would probably be useful enough that some people would want to pay to have access to that data.
I was wondering if there are any websites that use the business model described above (get small websites to sell you their data, and sell the combined data to other corporations). If anyone knows of such a site, it could be an interesting revenue source for webmasters. And if there is not such a site, then it could be an interesting idea for anyone wanting to start a business...
NOTE: I'm asking this more out of curiosity than because I actually want to sell my user's click data (though I might consider it in the future).