My profile wall is littered with Osama photo/video posts, why doesn't Facebook have tech in place that stop apps when their post frequency to walls gets out of hand?

They can use design solution, folding messages from one app to single message

>why doesn't Facebook have tech in place that stop apps when their post frequency to walls gets out of hand

Because Facebook is an advertizing platform. Apps can send as much garbage as they want and you can just ban the app from from your feed.