Police and campaigners also said internet firms must now start taking a proactive role in protecting victims from sex crime.
Detective Superintendent Louise Raphael, head of the national rape task force at Police Scotland, said her team had seen an "emerging trend" of women becoming victims of rape or sexual violence after meeting their attackers online.
Raphael said her team was "seeing a significant number of rapes" reported where two people have met over the internet, "whether that is a dating site or some other social networking site". She said of the sites: "I'm not here to dent their business. But I do think there's more they can do to help mitigate some of these things and alert people to some of the potential risks."
The first step, Raphael said, would be for sites to put a strong personal safety message on their home page, or advise people when they sign up.
"The reality is women are meeting up with people they don't know … women are finding themselves in a very vulnerable position."
She said she had "no doubt" sex offenders were using the internet to carry out crimes, adding: "The nature of the whole internet dating scene lends itself to those who would want to use it to target vulnerable people."
Victim support group Rape Crisis Scotland's latest campaign will also highlight the risks of online sexual abuse. The organisation has dedicated part of its website to tackling the link between the internet and sexual violence.
Katy Mathieson, helpline manager of Rape Crisis Scotland, said its team realised last year that there was a growing issue of internet-related sex crime.
The organisation recorded a 46% increase in the number of contacts from victims during 2012-13, compared with the previous year, with many of those crimes linked to meetings arranged online.
Eileen Maitland, an information worker with the charity, said people should think twice about what details they post online, such as mobile-phone numbers. She added: "We're talking about being careful about privacy and being cautious about the step between online contact and real-life contact."
George Kidd, chief executive of the Online Dating Association, said it had a code of conduct for member sites, including Match.com and eHarmony, to follow. He said the organisation was willing to work with police and action groups to improve safety.
He said: "If you consider that online dating accounts for one-quarter to a half of all new relationships, and tens of millions of people are signed up, then there are risks there, in the same way as going to a pub. Members of the association do look at people when they join the service and try to ensure that the website is as safe as possible."
Facebook was contacted for comment, but declined to do so.