Nearly one in ten (nine percent) web users have never met a quarter of their online friends, says Geomium.
Research by the location-based service revealed that phenomenon of 'faceless friends' or people that are part of an online friendship circle but have never met face-to-face.
"These are worrying findings – social networks are meant to facilitate socialising, not replace it," said Geomium CEO, Michael Ferguson.
"The idea of only communicating online is one that many people would be uncomfortable with. Social networks can be a great way of staying in touch but you can't beat actually meeting people."
More than a third of 18 to 24 year olds said they couldn't imagine a world without social networking while four in ten said social network sites were the main way in which they organise their social life.
However, just one percent of the over 60s use social networks to organise their social life.
"Use a social network to organise your social life by all means, but don't let it become your social Life," Ferguson added.
Geomium, which was launched last month, lets web and iPhone users discover where their friends are currently located, as well as lists of nearby restaurants, bars and events as well deals on food and drink thanks to a tie-in with Yelp, Qype and Eventful. All of these can either be viewed in a list format or on a map.