[derefr]

How about a history-based search engine? A plugin that simply submits every link you visit (when your privacy features are off) to the aggregator, along with how long you kept each page open before you closed it/surfed away. I know it would be incredibly invasive, but it would basically be a Nielsen Box for the Internet.

[frossie]

I don't think you can do that just via the history. A lot of pages are just sitting there in my tabs because I am not paying attention to them, not because I am engrossed in them. You need to be able to see what the user is really doing.

I remember a while back in the UK there was a study to actually measure real attentiveness while the TV was on. Cameras were installed inside people's TVs to record the viewers so their focus could be noted. This was all very clearly explained to them, but as time went by, and people being people, they eventually started to forget the camera was there; so in some cases the poor researchers got a bigger share of, err, domestic activities than they bargained for.