[foca]

Well the obvious reason is mentioned in the article: most people already do have a facebook account, while G+ is still new for most of the internet.

If you are likely to be on facebook, you probably already are. I don't think it's surprising the growth is decreasing.

I would be (pleasantly) surprised if the growth was negative, but that's not going to happen :P

[nextparadigms]

Actually, they are losing users in the countries where they first emerged. But for now, growth is sustained by late-comers in other countries, much like it happened to RIM.

http://www.insidefacebook.com/2011/06/12/facebook-sees-big-t...

I think when your core users and initial early adopters are leaving your product/service, you need to start worrying immediately, rather than wait for that 3-year late "financial impact" to "believe it" that you're in trouble.