I've never had problems with CCC myself or AMD drivers in general with my HD 4850. My guess is that people are overclocking through CCC. I have heard instances where CCC actually overclocked systems without a user's knowledge, but that may have just been a user who did something without realizing it.
I've also been told that the 4000 series was the last truly stable series AMD released, so that may be part of it. I know 5000 and 6000 cards had some buggy drivers when they were first released that have since been fixed for the most part.