The ability of Twitter to police rogue usage is minimal. Many times their posts fall in “grey” areas of offensive versus inoffensive content, making it difficult to moderate. In most cases, deletion or inactivation of accounts happens much after the damage has occurred. This does not prevent the perpetrators from establishing alternate or slightly different twitter id’s to resume their propaganda. Most of these rogue accounts cannot be acted upon by law enforcement because those countries from where they operate do not have effective law enforcement or they do not consider it a crime yet.
Inciteful posts have high impact, and are often unsubstantiated. Being public broadcasts they rapidly go viral and reach a large global audience. Posts such as those sent by ISIS have been effective in influencing youngster to join their ranks from across the world. Youngsters, taken up by these messages sign up for a cause from which there is no return even when the harsher realization dawns.
Governments, have an active interest to not bar these tweets, as they form a rich source of real-time information, in many ways more useful than covert intelligence. Sympathizers in countries with effective law enforcement may put themselves into trouble, if they draw attention through retweet or likes. Of late, governments have attempted to spread counter messages to negate the effect of these broadcasts.