One behavioural tendency that I find odd is how people with whom you are talking in person often expect you to break off your conversation in order to answer any telephone call you receive. In some cases, people have told me they feel that they are being rude to the caller by maintaining your attention.
To me, this seems like a misunderstanding of both politeness and the nature of telephones. While phones are conduits for communication, their existence does not create an obligation to answer at all times. Indeed, when one is already occupied in an activity that should be the focus of one’s activities, it would seem that politeness decrees that the call be ignored.