Suspected fraudsters and sex offenders are among those being reported to Scarborough Police - by their own Facebook “friends”.
Dodgy activity on social media sites such as Facebook and Twitter resulted in a dozen allegations to North Yorkshire Police last year from suspicious followers and friends.
However the force admit that figure could be even higher - as police may have misspelt the names of the hugely popular sites when recording the crime.
But The Scarborough News probe has found that the number of social media police investigations almost doubled last year.
And with the growing popularity of social media sites such as Snapchat and dating app Tinder - in which users “swipe” away possible suitors they don’t find attractive - that figure could rocket again in coming years.
North Yorkshire Police have advised web users to be extra vigilant in case they spot criminal activity on social media.
And a spokesperson added: “Social media is an amazing communication and information-sharing tool, but there can be risks involved if you drop your guard too much or fail to understand the way these sites work.
“As with anything in life, people should take the necessary security measures to protect themselves when they use the internet - whether they’re buying or selling online, using social networking sites or simply browsing.
“By taking some simple precautions, you can minimise the risks to you and your family.”
Our probe found that 12 alleged offences had been reported after web users claimed to have spotted illegal activity on Facebook, Twitter and photo-sharing site Instagram.
These figures include the case of Eastfield teenager Jordan Scott, who kicked and punched a cyber rival following a Facebook feud.
Violent Scott hit his ‘net nemesis with a cheap shot before sticking the boot in - but he was brought to justice when his victim logged onto Facebook and found a video of the New Year’s Eve assault posted by an onlooker.
Magistrates told Scott that only his early guilty plea saved him from jail for assaulting his young victim.
Figures disclosed by the police showed that for the social media crimes reported between May 2013 and May 2014, a suspect was either arrested or charged in a third of them.
And ongoing police investigations are still taking place in a third of all cases reported in the last 12 months.
Previously, North Yorkshire’s Police and Crime Commissioner Julia Mulligan has warned of the dangers of social media sites - and even branded Snaptchat “evil”.
At a public Scarborough meeting, the elected crime tsar admitted scouring her daughter’s Facebook page to see who she’d added as a friend - claiming it was “responsible” parenting.
A North Yorkshire Police spokesperson added: “We would encourage everyone who uses the internet to visit our online safety centre at www.northyorkshire.police.uk/onlinesafety to keep up-to-date with our latest security advice and guidance.”