Manners Maketh Machine
Users prefer polite computers, according to this article from the New Scientist.
This is something I bang on about when we're talking to our clients about design: that overall tone is important, particularly for mobile phone applications which are:
(a) not perceived as being computers (I overheard a friend of mine this weekend talking about how phones are "practically computers' these days).
(b) used by people who will be frightened or intimidated by technology; despite wishful thinking from some quarters about operators becoming pure data pipes, they perform a valuable function of bringing together complex devices, radio networks, and billing relationships and presenting these in a (reasonably) consumer-friendly way.
Want more convincing? Read The Media Equation, an excellent book which Jay recommended to me years back and which delves into how people react to machines and computers.