Don't know if this is true or not, and if it is, I don't know if it's true outside of Britain:
One thing I heard when I was at college was that taking an AIDS test could increase your insurance premiums, because clearly you're the kind of person who has reason to be worried about contracting AIDS. Therefore, people recommended giving blood, instead; they'll screen you for various nasty diseases (including AIDS) and you find out without ever having actually sought out a test...
Anyone know if there's any truth to that?