Originally Posted by r-dub
From my experience as a wrench, I think chains are super-tough and can take massive amounts of stress applied in the correct direction. Properly maintained, they will never break during their service life (that is, they will stretch past the place where you should replace them before they will fail.) Lots of folks (including professional mechanics, sometimes) abuse chains and then ride them. The most common is to put a chain back together w/o the proper tools or preparations and drive a pin into one of the plates. Pressure in this direction can seriously weaken a link, and when you apply lots of force to it (like accelerating in traffic) it will come off. Inspect your chain for cracking around the pins and be super careful when driving pins and your chains will never fail you.
ive never had a chain break either. if you take care of it it's all good, i think the biggest problem with people's chains is faulty chainlines and having the chain put together bad (pin not all the way in). ive seen a lot of people not put the pin in right, i know a lot of people don't clean/lube they're chains too. this shouldn't be a fixie problem and if it is, get a brake.