Something that could always happen for real.
Not just failures. If you fly in windy places it's pretty common for the auto-pilot to hand things back to you when it gets rough. If you then muck around trying to get it back in the best you can hope for is a missed approach....time to hand fly.
Every time the basic premise of this thread is trotted out, a cast of thousands flock to the site to extol the virtues of hand flying with a nationalistic style ferver akin to Americans draping their cars & houses in flags in an effort to be seen as the greater patriot, which itself is born out of a fear of being judged a lesser patriot than their fellow countrymen.
There may be a bit of this going on but in my opinion it doesn't stop this from being a valuable thread. I have thought more about it and assessed my own skills as a result of following the thread and I'm sure many others have as well.
A worthy topic for debate.