It seems that the Audience Network is not restricted to the US or English-speaking countries. This would be huge for European publishers, being the first real alternative to AdSense.

Here's a quote from the AdWeek article [adweek.com]. It's a must-read for all publishers who sell advertising on mobile sites.

"When I think about what we've been learning in the time spent with advertisers and publishers, it's that the importance of reaching people and not cookies is really starting to become something that people are seeing true value around," said Brian Boland, Facebook's vp of ad tech. "So, the success that we've seen on mobile is beginning to solve the problems of how you can make sure that the right person receives the right message."

Ad inventory will include banner and native ads on publishers' websites. According to Facebook, native formats now make up more than 80 percent of impressions through the Audience Network and perform as much as seven times better than standard banner formats....

...Earlier this month, the company revealed it had a $1 billion annual run rate during the fourth quarter for advertising spending, with the majority of that money going to publishers.

Discussion is in the Facebook Marketing Forum [webmasterworld.com].