It always surprises me how many times pilots do this, from broadcasting on guard by mistake, to not switching freqs, to doing cabin announcements on the freq, is it that easy to do? I have really no idea how their comm systems work, I always say something like "you forgot to flip the switch" and they move on to the next freq.
As for us controllers we sometimes get mixed up with our override on the landlines, as you have to key up if you call a sector, but you don't have to key up if you get called. The confusion usually for me sets in when I called someone then get called and hang up but still key up or if one of the ring lines calls, as either side can hang up and then you can be keying up to keep talking but the other side hung up and now you are hot on the freq. Always a big doh! when the flight you are talking about calls asking if you were talking to them, when you were just coordinating something about their flight.
