Tires routinely blow out but we cant expect a bike shop not to sell us a bike because it has tires. I do understand your frustration and have to assume (never a good idea) that it is more about being talked down to then the actual chain case breaking. It would be nice if people would own up to their mistakes but yet every day peoiple are whinning about being out of work but dont go look for a job or, and my favorite, the bank loaned me to much for my house and now I cant afford my mortgage. Please dont take this reply as rude or mean, just trying to see both sides. And if I missed something your story and the shop is infact incompetant, than atleast you know not to go back