This recent spurt of articles about how Facebook is supposedly declining is based entirely on the Facebook self service ad tool as far as I can tell. An initial study of the numbers that the tool was reporting back was compared more recently and the differences supposedly indicate drop off in numbers.
None of the subsequent articles that I've read seem to mention how the data was gathered, just that Facebook has lost X amount of users in Y country. I for one dont think that Facebook's publicly accessible ad tool is a very sophisticated or accurate way of measuring FB's user numbers.
And Facebook themselves has said the the tool (which they own and maintain) provides a provides a useful sample of data, not a comprehensive data set. This is much the same way that Google Adwords estimator tool works.
They also fail to mention if it's a net loss. Sure, 6 million accounts were closed, but if 60 million new accounts were opened in that same time period, then there's not much point in worrying.
