A 43 year old man was arrested on suspicion of tweeting the name of a girl who accused Coronation Street actor Michael Le Vell of rape.
Phil Davies, from the Greater Manchester Police, said public identification of sex abuse victims - in particular child victims during court proceedings - can "cause both immediate and long term distress and harm, especially in cases as serious as this".
Michael Le Vell, real name Michael Turner, denies 12 charges, including five of rape, the BBC reports. The actor played car mechanic Kevin Webster on Britain's longest running TV soap.
Davies said disclosing names on social media is effectively the same as through the mainstream media.
"People may not understand that when they use social media they are required by the law to keep victims anonymous in exactly the same way as people who work in mainstream media," Davies said.
The point about social media has surfaced again and again - Twitter is essentially a public domain, even if you have privacy restricted your account - and posting online can provide more unwanted exposure than shouting on the street.