Exact numbers are not available, but there has been a big trend for high profile people to leave Twitter in 2012. Some recent names include Lily Allen, Charlie Sheen and Alec Baldwin. Others have decided to stop tweeting themselves but to hand over control of their accounts to publicity specialists.

The main reason they are doing this is because of the increasing number of abusive or aggressive tweets they are getting. One of the first celebrities to highlight this problem was Stephen Fry, who even left Twitter in 2010 although he later came back to it. But many celebrities, and ordinary users too, are appalled at just how vicious the comments can be, and don't want to expose themselves to abuse.

Others, like Ashton Kutcher, have made mistakes on Twitter like posting an embarrassing comment, and decide to give up or get someone else to post for them. The trend is likely to grow.