A lot of people do seem to talk over other people and butt in to conversations. Sometimes it doesn't bother me; if I'm saying something that's just trivial anyway then I don't tend to mind too much if somebody else barges in with something more interesting. It annoys me more when somebody talks over the person I'm listening to -- then I often will make an active attempt to stop person B butting in (though making it clear I'll be happy to listen to them when person A has finished). I always feel very teacherish for doing it, though.

Worried about saying any more about this because I suspect I'm dreadful at this kind of thing and as such have barely even a high moral shetland pony from which to cast stones in glass clichés.