Not really. Everyone on this site has worked in software development at one point, right? So everyone here has written a bug before. Its reasonable to expect every piece of software (short of the stuff on the space shuttle) to have bugs. It simply isn't feasible for most software companies to find and fix all of the problems with their products.

Facebook, like all other software, is bound to have bugs. If you don't want your personal information/conversations to be exposed by a potential bug I'd suggest not using the service.