Inside Facebook said Facebook in the "United States lost nearly 6 million users, falling from 155.2 million at the start of May to 149.4 million at the end of it. This is the first time the country has lost users in the past year."
US wasn't the only place losing users, "Canada also fell significantly, by 1.52 million down to 16.6 million, although it has been fluctuating around that number for the past year. Meanwhile, the United Kingdom, Norway and Russia all posted losses of more than 100,000."
They posted the top gaining countries:
Webmasters and SEOs are discussing what is going on here. Supposedly, the data Inside Facebook uses to get this data is from Facebook's advertising tool. The tool may have reporting bugs leading to issues with these marketshare reports - so it is hard to be 100% positive that Facebook lost 6 million users in the US market.
That being said, a WebmasterWorld thread has some people saying they are not surprised. They feel Facebook is becoming too commercial and at the same time people are leaving because it is overwhelming and too time consuming for users. Meaning, people want to focus more on work and less on social things.
I am not too sure.
Forum discussion at WebmasterWorld.