What kind of bike was it? To some extent you have to figure you will break bits off as you ride more and more. On my Electra I ultimately broke everything from spokes to cranks to seat posts. Finally the steel frame gave out after a year of riding and cracked. But I figured it was OK as long as the bike was breaking not me. Now I've lost quite a bit of weight after all that riding and it's less of an issue. Nothing on my new Marin has broken.
I bought both the Electra and Marin new from a LBS. It's more $$ than craigslist, but the frame and limited parts warranty are important if you're going to be breaking stuff.