I've heard of many problems with fin rudders falling off but once you put a bottom plate and pin on it it's almost impossible. Even without falling off you can have major problems. A friend was making a turn under engine inside a small turning basin. Spade hung rudder hit a bottom object during the turn, bent the shaft and couldn't turn it. If he had a skeg or keel in front in all likelyhood would have been fine.

On the other hand, many times I curse my skeg hung rudder when backing as I have almost no control. All because of junk in front of it. If it was a blade I'm sure I'd have steering in reverse.