FSF takes on Apple's App Store over GPL

But that is just it, you can't really expect them to. The liability shouldn't be on them to do that (as is the case for Best Buy), but in the person that is submitting the application. What they should do (and I'm pretty sure they do it) is to ask the submitter to make sure he has the right to sell that app through their store, including distribution licensing issues. And in the case where they find out somethings wrong has been done, they take action (just like Amazon did, but poorly, on the 1984 book case for the Kindle).