Social networking website Facebook has brushed aside the Inside Facebook report saying the actual growth has been measured as a 21 percent in Facebook users in the United States in May.

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, Facebook said in a statement.

Inside Facebook had reported that Facebook has lost 6 million US users last month, tracking a decline in the growth over the last two months with an addition of 13.9 million users in April and 11.8 million users in May.

In the U.S., total active users fell from 155.2 million at the start of May to 149.4 million at the end of the month.Users in Canada have dropped from 1.52 million to 16.6 million, while the U.K., Norway and Russia also posted drops of more than 100,000 users, the report said.

By the time Facebook reaches around 50 percent of the total population in a given country (plus or minus, depending on Internet access rates in that country), growth generally slows to a halt, Inside Facebook's Eric Eldon said in the report. So far, Facebook has been able to make up stalls and losses with big gains in heavily populated developing countries like Mexico, Brazil, India and Indonesia.

Recently, Facebook has been charged with violation of privacy issues, the latest being the opt-out facial recognition software that identifies and tags Facebook users in photos without permission or forewarning.

From my experience, I get the sense that being on Facebook is not cool anymore, Hoglund, CEO of Law360.com said. The early adopters and trend-setters are moving away. [But] these are also exactly the type of people brand advertisers want to reach; if they are leaving, it doesn't look good for Facebook.

However, Facebook said it is very pleased with its growth and said in the statement: More than 50% of our active users log on to Facebook in any given day.