LinkedIn was the favourite social media site for professionals at work in 2009, with 86% of worldwide internet users referring to it, a jump of 24% on 2008.

The survey from internet security firm FaceTime Communications shows that most professionals use LinkedIn to network with colleagues (79%), to learn about colleagues (66%) and for general research (61%). Only 37% were using LinkedIn for marketing to customers.

While only 13% said they used Twitter in 2008 for work purposes, the number leapt to 76% in 2009, overtaking Digg, Delicious and YouTube in the professional social networking pecking order though these also experienced substantial increases.

Facebook is still regarded as mainly a personal social networking site and in another survey reported in eMarketer, by Liberty Mutual, three quarters of employees thought it was unacceptable to check Facebook at work, though nine out of ten in the FaceTime survey confessed to doing so.

Personal email however is seen as much more acceptable with two thirds of US users polled by Liberty Mutual having no problem with it.