Here’s a thought. With the rise of AJAX applications this is bound to happen, and may very well have been implemented somewhere, even though a quick search didn’t reveal a lot. So here goes:
Similar methods have for a long time been used on some sites (including my own Spurl.net) to track clicks on links. A very simple script could also log how far down a page a user scrolls, over which elements he hovers the mouse and even infer how long he spends looking at different parts of the page and probably several other things usability experts and web publishers would kill (or at least seriously injure) to learn.
Even though it’s nowhere near as precise as the famous eyetracking heatmaps (here’s the one for Google’s result pages), it provides a cheap method for web publishers to help better position ads and user interface elements, experiment with different layouts, etc.
Does anybody know of implementations like this? Does it raise some new privacy concerns?
P.S.: I just saw that Jep Castelein of Backbase posted some related thoughts this summer.