Careless tweets have landed a host of celebrities in trouble in the past with comedian Alan Davies, Sir Bob Geldof's daughter Peaches and Sally Bercow all finding themselves in legal difficulties due to their online posts.
Social media users have also found themselves in contempt of a court - nine people admitted naming the woman raped by footballer Ched Evans on Facebook and Twitter.
They were all told to pay the victim £624 each.
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Sir John rejected the PM's Brexit vision as "unreal and over-optimistic" as he accused negotiators of "souring" the atmosphere for talks.
Lively start to the week
White House budget officials outlined the information during a telephone call with reporters given on condition of anonymity.