When did I sign up for this?

I don't remember ever signing up for Twitter, but lately I keep getting emails saying LustyLady is following you on Twitter, Coocoomcgee is following you on Twitter, President Obama is following you on Twitter. Why are they following me? It's scary. I don't follow people because after awhile they would think I'm stalking them. I'm not a follower damn it. And I'm not even on Twitter!