Though finding a good used bike might not be too difficult, I think that finding the RIGHT used bike, what you want and in your size, could be very difficult! In my case, not too many people (if any) are selling their Rubies with higher end components in a 54cm size. In fact, I had to drive two states away to even try one with Ultegra in my size. I just couldn't judge how comfortable I'd ultimately be by trying the smaller frames that the shops had, and didn't want to commit to ordering the larger size when I wasn't sure what components I wanted.

People sell their bikes usually to upgrade, so lower end bikes are easier to find. And certain types of bikes - hybrids, mountain bikes, are more prevalent in the used market.

But once again, if you are getting a carbon frame for under $1500 it's a steal!