I have never ever given out my surname or address on messenger. But from one person I have been talking just general conversation for over 2 years now asked me if this was my surname. I havent replied yes or no just wondered how your surname can be found when you definately have not given it out.
If its yahoo messenger it sometimes displays the info you used to sign up the account when it sends messages etc - I've removed my surname from my yahoo account details for this reason.