I think if we all put together a list, it’s going to be easy to identify these troublemakers and avoid them. Actually, a better question would be what are the activities that get the most bang for your time, but they may vary a lot from discipline to discipline. Straightforward application of Pareto’s principle should go a long way.
By the way, is any of you keeping any kind of log of where your time goes? Or running any application like rescueTime?