Why do random people I don't know start following me on Twitter?

[CrashCondon]

I'm not famous or important at all, just a schlub mining fantasy football info.

Are they all twitter spam bots or something?

[Billy Driskell]

some are spam bots and some are poeple that like your updates. some are just peolpe that look for twitter friends cause they dont have many friends in real life.

[psych_78]

Well not sure if you noticed or remember but when you first join, Twitter adds other random twitterers to your account (I suppose to get you started). Maybe this is why you are getting new followers, or alternatively people are finding your tweets interesting and are recommending you to their friends.

[Jadowa]

These are probably people that are actually looking to get followers. People will start following you in hopes that you will in return follow them. Most of these people want you as a follower to try to sell something to you, to get traffic to their website, etc.