Marketing Land, 26 Jan 2012, Danny Sullivan: "Until now, Twitter’s not had the ability to censor certain tweets or accounts, to prevent them from being seen — if legally required — by users in particular countries. That’s now changed, though Twitter stresses that it hasn’t yet used this new ability and that should it have to, anything withheld will be disclosed. Twitter has shared the news on its blog, saying: 'As we continue to grow internationally, we will enter countries that have different ideas about the contours of freedom of expression.' ... Twitter is preparing for potential demands in the way that Google already does, by alerting its users to when content has been withheld and providing information about why, through the Chilling Effects site."

At present, a US idea "about the contours of freedom of expression" is the Smith-Mundt Act ban on the domestic dissemination of US public diplomacy and international broadcasting. Twitter's new capability allows this law to be observed. Even if all USIB content is blocked to US IP addresses, many of remaining USIB shortwave broadcasts will be audible in the United States. That is, until those transmissions end. When that happens, enforcement of the domestic dissemination ban will be complete.