Politicians are well aware of the campaigning power of Twitter. Which explains why Boris Johnson appears to have changed the name of the non-partisan @MayorOfLondon Twitter account to -- you guessed it, @BorisJohnson.  Changing the account instantly gives the Mayor 253,152 followers.
This matters because the Mayor of London account is an official tool of the Greater London Authority, used to communicate with the public. Taxpayer money will have gone towards it in the form of staff time spent manning the account. Now that the name has been changed, the embedded link on the page has been changed from the neutral www.london.gov.uk  to Boris's campaign website, www.backboris2012.com .
Over at Liberal Conspiracy, Sunny Hundal,  who reported this story first, points out that Gordon Brown established the No 10 Downing Street Twitter account but didn't change it to his own name when he stepped down.
The BackBoris2012  website has published the following statement:
As some of you may have noticed, earlier today Boris changed the name of his Twitter account from @MayorofLondon to @BorisJohnson. While the name of the account may have changed, rest assured that the account is still - and has always been - controlled by Boris.
No City Hall resources will be used to update or maintain the account - that would be against the rules. Given we're now in the official election period, this change is being made so there can be no question of Boris using official resources to campaign.
Of course those who no longer wish to follow the account are of course welcome to "unfollow" at any time.