The LinkedIn study found that a third of the UK admit they feel obliged to add a professional contact to their virtual social circle.
And they worry mixing business with pleasure will cause problems if bosses and colleagues see personal information, false claims or embarrassing pictures posted online about them.
But despite this, so-called "Frolleagues" - a work colleague you add as a web friend - are on the rise even though seven in 10 Brits believe it is important to keep the two separate.
Frolleagues are now becoming so prevalent that the Oxford English Dictionary is considering it for inclusion in its next revision.
"It's becoming increasingly important that we keep our professional and social lives separate and manage our online reputation as effectively as possible," The Sun quoted Cristina Hoole, of LinkedIn, as saying.
"There have been plenty of stories lately involving the type of behaviour that is completely inappropriate for a work environment - people need to realise that even virtual actions can have very real consequences," Hoole added.
Jo Bryant, etiquette advisor from Debrett's, the experts in modern manners, added: "Always employ your usual good manners when online. Work out who your true frolleagues are, and remember that social networking is meant to enhance your social and professional life, not obliterate it."