Twitter is contesting a US court order requiring it to turn over the message history of a user who had been charged with disorderly conduct during the Occupy Wall Street protests in New York last year. Protesters around the world have relied on Twitter to organise and disseminate information during demonstrations. Twitter claims that it's terms of service means that users retain ownership of the content they publish and it wants to stay out of such disputes. It claims that as with any internet service provider it is the people that upload material that are responsible for issues of copyright (and) libel for example. In the US the Stored Communications Act requires a service provider to disclose certain kinds of electronic communications without a warrant. In the UK The Regulation of Investigatory Powers Act 2000 (RIPA) regulates how certain public bodies access a person's electronic communications which usually involves the production of a warrant. However see Home Office proposals to enable access to communications on demand highlighted here "Email and web use 'to be monitored' under new laws".
For FE and HE institutions who publish user generated content the position remains that by removing potentially libellous material posted as soon as possible, once notified, this can protect against being held liable for its publication. Complying with RIPA warrants will also be necessary.
Further details of the Twitter dispute can be found in the BBC story.