For personal details I often provide a whole load of crap. Tell them you are ethnic, don't speak english as a first language, are at college, living at home, in a household making less than $25,000 per year, don't drive a car, etc etc. You will never hear from them again.
Computer "researchers" are another crowd I give a load of crap to. Nothing I enjoy more on a slow afternoon than messing with their heads. "E-mail ? No, I can't say I have ever heard of it." or my favourite "Oh, I don't think the internet is going to catch on, we are waiting to see how that goes."