I agree with Peter and OM on that.
It's like rock-paper-scissors, while the feel has no resistance to misfeel, you can detect the later with a detect magic, or cancel or dispel it.
If faced with two casters, one using something like presence, while the other detects magic, you'd be jammed up (much like someone invisible faced with a foe looking, and detecting magic).
Throwing a non-detect on top makes for a nasty combo, since the detect magic won't work either.