Anonymity is not the same as privacy. Tor is more about anonymity than about privacy.

That exit notes can sniff traffic has been known for a long time. Compromised exit nodes do not compromise anonymity as long as you don't give up personally identifiable information in traffic that gets routed via exit nodes.

More problematic is that compromised exit nodes could inject or run man in the middle attacks on your outbound traffic. These could then make you give up your real IP. This is why you shouldn't run exploitable protocols when exiting via Tor (ie. don't use javascript, flash, etc. if you want to remain anonymous).