Those are the reasons I don't like them (although I haven't run for years so it doesn't actually affect me!) Also if you're in a big event it seems a shame to shut out the noise from supporters etc.A lot of races, particularly the ones with big participant numbers, do ban them. They usually say for safety reasons - you might not hear instructions being called out by marshals etc. I think it can also cause a lack of awareness of others around you, people trying to overtake etc.