I've had two babies well over 9lbs and c/s was never even discussed as an option. IMO the biggest problem is the size of the shoulders (my last got a bit stuck and dr had to help her out) and not so much the weight.
I think that in some larger hospitals they are too keen to suggest c/s as an option to try to reduce event of emergency c/s. A woman due at the same time as me (both having #1) was going to a larger hospital and they convinced her to have a c/s because the baby felt large, and she was only 8lb.

sherieb