Ask HN: Why hasn't craigslist taken issue with chrome extensions?

They can, doesn't mean they want to or will.

It's harder because the violation is coming from the user. Padmapper was hitting their site with their equipment.

Also, it's less of an issue because CL still gets the visits -- the problem with people taking your data is they siphon off your users. CL needs to cut off anyone who is rehosting data in any way before it becomes a problem.