He's such a private person, I'm not surprised that he's eliminating as much shrieking fans (not saying you are, I'm just generalizing here) as he can.
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Well, the "shrieking fans" are human beings, with feelings, and perhaps a misunderstanding of who he really is, but never the less they have feelings.
I'm not sure that blocking them is the way to get rid of them, actually.
2 things about Twitter:
1) there is a HUGE difference between a commerical account and a private account.
2)Twitter assumes that the user has some respect for human fraility. This is a HUGE assumption, and the main flaw in the system. You rely on a person to have that awareness of how far is too far.
Design wise, it's a great system for communication, especially between coworkers, family, a special interest group, etc. Any place where you are not using it primarily for social control of the individual.
It works better when you know the others, and want what is best for them.
I've given all this alot of thought.