Another great example lately is Reddit. Reddit's mobile experience had become awful. Every time someone sends me a reddit link and I click on it, I'm taken to Reddit's mobile site, which should function just fine and dandy, but the minute it detects you are there on a mobile browser, it spams you with "Reddit works best in the app!" messages, and won't let you view some subs at all without signing in.
Reddit is a great example of mobile done wrong. Don't be like Reddit.