I think you're onto something. I also think this falls into investigative journalism - which used to be able to drum up funds for that sort of cost.

There are all sorts of problems like this. What could you learn from the browsing history of people that work in sensitive areas? i.e. nuclear facilities, national labs, financial/industry regulators, etc. City and state representatives probably give away a lot through browsing. There's plenty of low lying fruit ripe for exploiting in huge ways.

Another avenue: merely knowing when someone is likely to browse the internet tells you:

-they're awake

-they're at home/indications of their location

-their level of awareness (think security workers or even prison guards)

Imagine being able to figure out the best time of day to hit a bank by browsing history? In an aggregate way you could probably figure out staffing (corporate level) or whether someone's home (residential level).