Facebook members reach 1billion, where will the next billion come from

The number of Facebook users hit 1 Billion last week.  It's an incredible number, although to be honest, I had assumed it already was there!

This article poses the question of where will Facebook find it's next billion users: Adage Article: Facebook Find Next Billion Users

In mature markets, Facebook has already nearly reached saturation.  Growth in the US has slowed to 2% and according to ComScore nearly 90% of 18-24 year olds and 61% of 65 and old adults are users already.  While there is some room to growth, these numbers will never pass 100% and for the older generations, there are likely limits to the user adoption there just in terms of the technological generational differences.

As you look abroad, however, there are some limitations to Facebook's growth.  Facebook is banned in China and in Russia competitor Social Network sights dominate Facebook by a factor of 10x.

For Facebook, Japan and South Korea look like emerging markets with roughly a quarter of the each countries internet users also on facebook.  There is room here for growth, but relative to China, these populations are not nearly as big.

To continue its growth in areas like Brazil and the Phillipines, where users are more active via their mobile phones, Facebook is aggressively pursuing mobile app and ad product development.

The article speculated that Facebook, who unveiled it's first brand ad last week, could also generate user growth through advertising.

While it seems that Facebook has fully penetrated the mature markets, and there is room for growth in other markets, to me, what is more important for Facebook is determining a successful monetization method.