Facebook membership has grown past the 250 million mark, increasing its lead over rival social networking sites by an even greater margin.

What's more, the growth rate is staggering, as Facebook membership topped 200 million just three months ago. Growth seems to be slowing down stateside, as almost everyone who had any interest joined up already, and the majority of new users are based in Europe, Asia, Australia, and it's now catching fast on in South America and Africa.

To put things into perspective, about 4 percent of the global population has a Facebook account. If Facebook were a country, it would be the world's fourth most populous one, right after China, India and the US. Tough luck Indonesia, have more babies.

You can see an interesting animation showing the growth trends and user density here, and it's basically spreading like a pandemic.