But what's really important and different to Germany is the organizational part on facebook. Our year has a facebook group to organize hiking and biking trips; all new graduate students are registered in one group and "official" announcements are posted there (e. g. campus tour tomorrow with the head of graduate studies). Of course, this exemplary event is not compulsory at all, but without facebook I would not have known about it.
The dancing group has got a facebook page, my sponsor in Germany, the Institute of International Education, George Orwell, everybody! To be honest, it's unbelievable pragmatic because otherwise I would receive a lot of mails...
Luckily I got a new smart phone which works properly in the US and a "cheap" prepaid plan or 30$/month. I finally exist in the US.
I smart phone, therefore I am.