When does a popular and spontaneous protest become mob rule? Fans of Twitter, the micro-blogging site, have chalked up a couple of notable victories of late. Followers helped to expose a legal injunction against The Guardian and Twitter-led protests generated tens of thousands of complaints against Jan Moir when she wrote a column using the death of Stephen Gately to criticise gay marriage. Is this net-based protest a valuable tool to demonstrate popular opinion or are we sacrificing traditional political engagement for the instant gratification direct action? Witnesses: Professor Andrew Chadwick of the New Political Communication Unit at Royal Holloway, University of London, and author of the book Internet Politics Brendan O'Neill, journalist, writer and editor of Spiked Online Nick Cohen, author and Observer journalist Ben Locker, 'Twitterer'.