Well I am just speaking from personal experience, you can lever a tire off the ground with a feeler peg, for me it was a combination of riding boots (steel around ankles) being bascially mashed between the peg and frame which did not give any and did not allow peg to fold. The feeler dug a huge gash in the pavement before the tire finally lifted (this was an off camber turn as well) and I have no doubt whatsover that it assisted in my lowside. I can't really see any benefit to having them either, if you are achieving enough lean angle to touch them down then you know your pushing your bike well before they touch so what good is it going to do you? Do you brake or stand up your bike when they scrape and change your line? I never did.
Edit: This happened at Deals Gap and I was riding very hard that day, was I going down before this happened, who knows but they were the only part of my bike dragging and leaving marks on the pavement. I had hit the feelers many times before this (pretty much every time I rode there) with no ill effects but I think the combination of riding boots preventing the peg from folding and that much wieght being put on the feeler had alot do do with it... I've had several crashes up there (4 actually all a result of pushing myself or the bike to hard) and not afraid to admidt when I dump a bike.