Technology critic, Bill Thompson, warns that comments posted on Twitter are not private and care should be taken when posting to the site. He discusses the misleading informal set up of online tools like Twitter and Facebook which encourage spontaneous chat and immediate reponses to comments posted. Previous private conversations can now reach a world wide audience with a traceable message trail. Institutions already using Twitter and Facebook as learning tools may wish to remind staff and learners to take care before they post and be aware of the potential consequences of careless comments directed to, or about other individuals. For the full article, please go to: http://www.bbc.co.uk/news/technology-10740954.