Twitter Followers & No Notifications

Every day I get a couple of followers I end up blocking. Today I got five.

They all have names like Buffy5782, that is "girl"+"numeric" username.
They never have a link on their Twitter profile. A normal 20-someting at least has FB.
They have few commercial Twitters during a week in their hisotry.
They have twitter streams that indicate more or less that they have nothing interesting to say.

AND when they follow me, I NEVER get an email from Twitter.com telling me about it even though I get notified when normal people follow me both before and after these mystery followers.

Why do I block them?

I guess it's just paranoia because I can't see an advantage for them unless it has to do with gaming some Twitter filter that uses community embeddedness for some reason.

Of course I get my share of "Marketing Professionals" who just happen to have a great application that can monetize my twitter stream and get me "millions of followers" and who can change my life et cetera. Meh.

I wish someone at Twitter would explain what is going on like Mark Cuban did when the spam-bloggers were messing with Ice Rocket.