An article on Joi Ito's site reveals that for the most part, when presented with a claim of copyright infringement, ISPs will take down a site without even checking the validity of the claim.
A Dutch civil rights group recently ran an experiment in which they posted an 1871 public domain text to domains hosted by ten different ISPs, and then sent copyright infringement notices - full of legalese - to each on behalf of a fictitous organization which allegedly owned the copyright to the work. Despite the fact that the notice was sent via hotmail, seven of the ten removed the material. Some ISPs did this within hours, and some failed to so much as notify the account owner. Of the ISPs, only one actually noticed that the text in question was public domain. The rest likely did not so much as read it. One of the ISPs actually sent the hotmail claimant the site owner's personal information!
It is indeed sad news that in today's world the fear of being sued is great enough to usurp justice. I can only hope that these ISPs have learned from this, and that perhaps others in the world will take notice.
A full text of Bits Of Freedom's experiment can be found here.