100px gives you around 70 zones in your average desktop window. More, when you consider shared hits between zones. That's enough to do basic heat maps of a web site (such as for ad impression tracking), coarse navigation, or integration into things like editors/IDEs.
I was thinking about ad impressions as well; but God forbid websites are ever able to use my camera for eye tracking by bypassing the webcam permissions (or through the removal of in the future? I expect anything when it comes to content monetisation).
