There was a time when Facebook was synonymous with social media, when it was the only credible competitor Google had and when it seemed that its growth would be, well, unstoppable. That time has now passed.

If that statement sounds strange on the day that Facebook, quietly, announces it’s passed the one billion members mark it’s because of that announcement. Let me explain. Facebook has taken a beating of late. Its IPO was disastrous, its customer service reputation is in tatters and, it seems from the supposed leaked private messages debacle, even its very image is suffering.

It badly needs a win and in terms of winning nothing makes a statement bolder than size. When it comes to social networks Facebook is big. So big as a matter of fact that if it was a country its population would be 3.1 times bigger than the USA’s and 12.2 times that of Germany’s. As a matter of fact its population would be 1.33 times that of Europe’s with only India and China being larger than it by a fraction.

While that is an achievement for a company that’s just eight years old the superlatives have to stop here because what really counts in social media is not size but quality. Having gone past the point where fan numbers and Likes were sufficient to impress we are now at the stage of social business where we need to have some real ROI. And that can only be supplied by engagement.

From ads that fail to perform to moments where content is pushed without authorization Facebook has patently failed to engage its audience in a way which generates real cash. The reason why lies deep in the company’s psychosynthesis. Facebook, as its tagline, says “… helps you connect and share with the people in your life,” and I will be the first to admit that it does that brilliantly well, in a manner which generates stickiness for the site and virality in terms of attracting others. But here’s the problem: Facebook has succeeded so well in being the world’s favorite hangout place that it cannot be anything else.

Having got its huge membership base by convincing us to connect to friends and family it now finds that we resist when it asks us to become the Facebook equivalent of Amway reps charged with selling products to our closest contacts.

As a matter of fact that resistance is such that over the course of the last twelve months Facebook membership barely moved in Europe and Australia and fell in the United States, areas which most companies aim to market to.

The bulk of the Facebook rise which took the company past the one billion members mark came from Central America, the Middle East and Africa. While this has some obvious long term advantages when it comes to reaching an audience based in those countries at a low cost, in the short term it is of questionable marketing value.

The conundrum Facebook faces is that its growth model is now out of step with the profit requirements being placed upon it by its shareholders. How it will actually handle this may well determine the company’s fate.