Ask Patents is for stopping patents from being granted. I'm suggesting a way to kill patents that are already granted + monetary incentives for the worst / most expensive offenders.

Not true, I've seen requests for granted patents.

Interesting!

Granted patents aren't re-reviewed, so someone would have to cough up a few tens of thousands of dollars to do anything with submissions on granted patents.

Is the concept that people are contributing evidence to be used should someone challenge the patent?

Indeed, as stated, askpatents is not just for new patent applications. It's got a bit of head-wind right now, and the more people that get involved the better.