Simple. Stay off Facebook.
OK, that's easy for a 50-something like me, not so easy for the online generation, but I only see risk. The identity-thieves out there are having a bonanza, thanks to social networking sites. Some of them are really quite clever, and you'd be amazed at what they can harvest from just a few sites - your name, age, gender, where you live, what you look like, where you work, the name of your spouse - even your dog's name. You might think, "it's alright. My info is spread around." but these people are like detectives - they look you up, then your friends, then your workmates pages..........Armed with this information and a bit of criminal guile, they CAN impersonate you.
So, if you're going to use social networking sites, just bear this well-intentioned advice in mind. Then write it off as the ridiculous imaginings of a stupid old fart. At your peril (cue fiendish movie laugh).