This is like the Spanish Facebook, very similar....and also Very popular. The name of the site i believe is a play on "tu gente" (your people), but i may just be making that up Tuenti was the most popular search engine term of 2009 so far following only "Michael Jackson" and "Facebook."
This statistical information however is from 2008 but it's still interesting:
Tuenti.com Domain Search Traffic
Tuenti Geographic Data
Tuenti Demographic Data
To spice up my life i have begun using it as of yesterday afternoon (i got an invite a looong time ago from a Spanish friend) and making friends on there, exchanging hello messages about mundane things like the weather,etc but it feels so nice to use my Spanish again, keep it fresh, and to talk with the locals of where i was.
It also is fun to talk with them because they think blonde hair and "light eyes" (mine are hazel but i guess that's light to them) are exotic it "rubia guapa!!"
If you have any friends in Spain or would like to make some, you should check it out-- Tuenti (click)