Not a whole lot, at least right now. 

- They feed into some analytics that mods & employees use to keep an eye on the general health of the sites.
- They're put into the public data dumps and [Data Explorer](http://data.stackexchange.com/) for perusal by all and sundry.
- They influence the selection of [Greatest Hits](http://stackoverflow.com/questions/greatest-hits). 

There *were* some 10K tools as well (now hidden) intended to help flush out posts that were getting exceptional amounts of anonymous feedback; we may bring these back in some form eventually.