Well, it is not extortion, since it is currently legal.
The Communication Decency Act, which is sort of turned on its head to permit indecent content without liability of the host of the site, provided certain steps are followed.
47 USC § 230 - Protection for private blocking and screening of offensive material http://www.law.cornell.edu/uscode/text/47/230
and specifically under that the following language which immunizes the posting of the information and allows them to voluntarily ( for which they charge) to remove it. Many say this is outrageous, but currently, it's the law:
(c) Protection for “Good Samaritan” blocking and screening of offensive material