[Goladus]

I think the hardest part is finding what behavior to track. Click-through is obviously bad. Bookmarking and passing to friends will also slant the stories in a way that isn't necessarily good. I have a lot of friends that don't really care about hacker news, and tend to bookmark more reference-type material.

Comments are useful, but that slants towards controversial topics.

[derefr]

Simple idea someone might want to found something on: provide a little highlighter extension for browsers/in a wraparound frame/as a bookmarklet. Track pages people highlight; title and describe them as the few most highlighted words.

[Xichekolas]

Not sure if I'm the exception to the rule, but I definitely highlight random crap while I read a page (just something for my mouse hand to do)... so I'd ruin your stats in a mean way.

[waleedka]

I do the same. Mostly as a way to quickly find where I was reading after a distraction.