Anyone with a Twitter account occasionally gets a random new follower. Some may be legit people just wanting to hear what you have to say, some may be cyber-stalkers :P, but MOST are just using some automated software that set's their Twitter account on "Auto-Pilot" and follows as many as people as possible. The goal is to hopefully get you to follow them back. I've heard that some "Twitter Friend Adders" can even target a specific group of people.
Does anyone have any experience with a Friend Adder? Have I even accurately explained how they work? If not, can someone please elaborate? And finally, are "Friend Adders" frowned upon by Twitter?