if this is happening from facebook, you can block this person from accessing any of your info, or from contacting you. they can also be reported to facebook as a nuisance, suspicious, etc., and facebook will normally block them or cancel that account. that wouldn't stop them from setting up another account, though, and trying to friend you again. just be very careful about the info you put out there. i know that it's supposed to be a "social network", but it can be used by anybody to gather info and intrude into our lives. be sure to carefully screen who you friend--the world is full of predators and cons, who are happy to take advantage of us, and frighten us, just for fun.