You are, by any standards, a modern-day literary colossus. Your novels are fat, fantastical, fatwa-inducing and famously difficult to finish. You've won the Whitbread (twice), the Booker and the Booker of Bookers; are photographed, frequently, in the company of wildly beautiful women much younger (and taller) than yourself; have been elevated to a knighthood by Her Majesty the Queen. What kingdoms remain for you to conquer, what realms still defy your dominion?

Well, Twitter, for one. Sir Salman Rushdie's first steps last week into the exciting world of 140-character communication were, to say the least, halting – not least because he found himself having to tweet under the ever-so-slightly mortifying username @SalmanRushdie1, his actual name having been usurped by a thus-far mute imposter identified as Jigar Gupta, who shows no signs of wanting to relinquish it.

"Who are you?" tweeted the peeved author. "Why are you pretending to be me? Release this username. You are a phoney. All followers please note." He then faced the indignity of having to prove his identity, answering a barrage of obscure questions from would-be followers about, among other things, his late sister Nabeela's nickname, and the sometime hiding place of the Pakistani poet Faiz Ahmed Faiz.)

Name-squatting is against Twitter rules, as is impersonation – defined as "pretending to be another person in order to deceive" (obvious spoof accounts are fine). But Rushdie is by no means the first celebrity to encounter the problem. There are countless fake Simon Cowells; @MossKate has 13,000 followers despite the real Kate Moss repeatedly saying she "doesn't do social networking"; @lilyroseallen changed her name to @MrsLRCooper when she married, only to see someone instantly take over her maiden name.

Kanye West famously – if, ultimately, regrettably – forced Twitter to evict someone tweeting merrily as Kanye West by complaining on his blog: "WHY WOULD I USE TWITTER??? IT MAKES ME QUESTION WHAT OTHER SO CALLED CELEBRITY TWITTERS ARE REAL OR FAKE." Angelina Jolie did likewise, but then sensibly locked her account and, to the joy of millions, has uttered not a tweet since.

You can't be too careful out there, you know. As that celebrated New Yorker cartoon put it all those years ago: "On the Internet, nobody knows you're a dog."