Facebook is losing users in the UK, US, Canada and Norway.

The social networking giant gained 11.8 million more users last month but the rate of growth is slowing globally, according to a study by Inside Facebook. While Facebook boasts some 700 million users worldwide, the number in core markets has dropped.

The number of UK users fell by 100,000 to 29.8 million users, a still astonishing 58 percent of the online population. In the US, the fall was more dramatic, withthe social networking site losing 6 million users in May, down to 149.4 million at the end of the month, just below 50 percent of teh online population. Canada dropped by 1.52 million.

A Facebook spokesperson, in an e-mailed statement, said Facebook is pleased with its growth. "From time to time, we see stories about Facebook losing users in some regions. Some of these reports use data extracted from our advertising tool, which provides broad estimates on the reach of Facebook ads and isn't designed to be a source for tracking the overall growth of Facebook. We are very pleased with our growth and with the way people are engaged with Facebook. More than 50% of our active users log on to Facebook on any given day."

Dan Olds, an analyst with The Gabriel Consulting Group, said he's not surprised that Facebook is having a dip in growth and he doubts that Facebook executives are worried about it. "The growth rate is naturally going to tail off when penetration gets that high. We're also going to see some ebbing and surging over time as the user base stabilizes and matures," he said.

"I don't think this is necessarily troubling for Facebook at this time," said Olds. "Some might see this as a sign of doom, but I don't... If there were a strong Facebook competitor that was growing at the same time as Facebook was shrinking a bit in the U.S., it would be a different story. But that isn't the case."