Guba is US-based.
When they start selectively removing access to content on their service, they lose their "common carrier" status (a legal principle, not an official title).
Since they have already started removing content, that privilege is gone.
They are now responsbible for the legality of any illegal content that remains (i.e. underage content).
This should be entertaining to see play out.
Oh, yeah.. references:
http://www.trageser.com/computers/online/1528.php (9-10th paragraph)
http://www.columbia.edu/dlc/wp/citi/citinoam11.html
http://www.gag.org/news/news_1998-95/2180fin.html
http://www.drmwatch.com/legal/article.php/3376301
http://www.cybertelecom.org/notes/common_carrier.htm