Yes, they have been known crash, freeze, and hang--more often than anyone wants to let on, but probably a lot less often than PCs doing the same things. In OS X, though, a program can hang, and you can step out of it to the desktop, where you can force quit the program and restart it without having to restart the computer. That works very well when the browser hangs, which a fairly common problem. Other problems,can come from running more applications than you have RAM for---t)his could be a problem for people with older computers who have upgraded to a new OS without adding RAM), and also from running an application that was developed for either a later or much earlier OS. I shamelfully admit to freezing up repeatedly when running a particular application in OS 8.6, only to discover that it was developed for 9.22--the tech support folks were amazed that it ran at all....

Nobodies perfect....