Two seperate issues here: fatigue life and denting. Any sub 2.5 lb frame is going to have a limited fatigue life and won't last forever if used hard for many miles.

CAAD7 is a very strong frame, according to the limited fatigue test data I've seen. And, Cannondale should be applauded for being very up front about the issue:

http://www.cannondale.com/bikes/tech/pdfs/115622.pdf

Of course, if a frame is good for say 30-40K miles of hard racing/training, I figure it will last me about forever doing club rides, centuries, tours for 3-5K per year.

Denting is certainly an issue on this super thinwall tubing. I really don't want a bike that's prone to damage just in normal handling, or if someone else leans their bike on mine at a rest stop.

Still, have to question why CAAD 7 lightness is appropriate for the consumer market. I think C'dale and the other major brands are in a tough spot here, since so many buyers just want the lightest thing they can afford, and don't even think about life/durability.