In my experience, bounce rates are tightly tied to the traffic source. Search engine visitors have higher bounce rates because that explains the success of Google in trying to get users to the exact information they are looking for. Direct visitors tend to spend a lot more time because they visit everyday to check out all that's new and so spend considerably more time and visit more pages.
IMO, news, entertainment, sports,etc. should have lower bounce rates. Feature websites that perform specific actions (eg: weather.com ) should have higher bounce rate.