mclean: Going back to the OP, I wonder if it's a form of station identification, which is a legal requirement for some broadcast radio transmissions. I think on US TV it's at least few seconds at the top of the hour. UK TV stations seem to do the same. Also radio stations here but more frequently than that. Just guessing.
My guess is it has to do with watermarking to protect copyright. Probably forced on broadcasters by the IP mafia. This makes it easy to identify the source of anything that has been copied. Of course it could also just be another case of mindless imitation. Someone somewhere started doing it as brand identification so everyone everywhere else wants to jump on the bandwagon. I have satellite TV and I am not aware of any broadcaster anywhere in the world who does not advertise their logo in this way.