Facebook's growth has become a thing of legend, but a recent report suggests it may have lost ground in parts of North America. The world's largest social network soared past its competitors to reach half a billion users in July 2010, and fueled by strong international growth, it's poised to reach 700 million users within weeks.

However, according to data from Inside Facebook, Facebook's growth in April and May 2011 slowed considerably. It gained 11.8 million new users in May, and 13.9 million in April — compared to a typical month in the last year when it grew by at least 20 million users.

Traffic data, especially coming from a third-party source, can be skewed for a number of reasons, but if Facebook's growth has slowed down in two consecutive months (and if the trend continues), it might be a significant pointer for the company's future. In 2008, Facebook started growing like a weed, surpassing expectations month after month, but at some point this tremendous growth will have to slow, especially in the most saturated markets like the U.S. and Canada.

Has that moment arrived? It's possible, but we cannot be sure just yet. We've reached out to Facebook for a comment on the data and will update the post when we learn more.

Update: Facebook gave us the following statement: "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 in any given day."