Doesn't crash, but sometimes apps seem to be created under the assumption their permission request isn't creating a popup, so there are sometimes like 10 in a row, so the user will often give up and just either blanket deny or accept

EDIT:an "allow for 10 min" option would resolve this

In my experience, the apps I've used don't crash. The biggest problem I've seen is me getting frustrated with an app for not working as advertised. Then I remember that I've enabled privacy guard and the app must not be getting some info it needs from the OS.

I think it can return valid data, like empty sets or fake data. So apps shouldn't crash at all.

Rarely, as it will feed empty data. It doesn't deny permissions.

If you have a rooted device, try XPrivacy. That gives you a lot more options and you can even set what data you want the app to see. Want those apps that are asking for your location to think that you are on the North Pole? No problem.