Not a bad idea. A recursive feature could be very useful.
However, I can absolutely see people adding "C:\" (recursive)
and wondering why they got infected. "I was having trouble with a few apps, but this way everything runs perfect!"
That kind of thing can't really be helped though. There is only so much you can do to protect people from their own ignorance, or dare I say stupidity?
Posts still pop up now and again with people running D+ or the firewall in training mode full time...