Really interesting article about Twitter having problems with the balance of anonymity: http://wrd.cm/1BKymte
They want to try and keep people safe in the Wild Wild West, that is Twitter, but the flip side would be catastrophic.
The essence of Twitter is how it connects the world, and allows us all to be civilian journalists. Cracking down on Tor users silences those who need a voice most. Tor helps to keep websites from tracking users locations. Their services let users publish web sites and other content without needing to reveal the location of the site.
This is a very controversial topic, but for now we stand on the side of Anonymous.