Asking User To Rate App: Is Apple Allowing Developers To Request 5-Star Rating Or Reward Users For Rating?

I’m trying to determine what Apple is allowing developers to do to encourage users to rate their app.  I’d like to ask users to give my app a 5-star review and then unlock some in-app content if they leave a rating.  

I know that some prominent apps have asked for 5-star ratings (Path, Draw Something), but I’ve also heard of others being not approved for this reason.  I’ve also heard of similar problems with unlocking content if the user rates the app, but I’ve also seen lots of apps that do that.

So, what’s the story?  Is it generally just a matter of which Apple reviewer you get?

Apple in general doesn’t want anyone gaming the rating system. 

Apple in general doesn’t want anyone gaming the rating system.