The novelty is wearing off. From the Guardian:
That means the site’s growth has slowed for the second month in a row, even as it approaches 700 million users worldwide.
In the US the site lost about 6 million users, from 155.2 million at the start of May to 149.4 million at its end, according to data gathered from Facebook’s advertising tool by the site Inside Facebook.
Canada fell by 1.52 million to 16.6 million and the UK, Norway and Russia all saw falls of more than 100,000 users, the site said.