Important social networks

Here is a shortlist of social networks I think we should look into...

Name	Description/Focus	Registered users	Registration
MySpace	General. Popular in the USA, UK and Australia.	217.000.000	Open
Habbo	General. Over 31 communities worldwide. Chat Room and user profiles.	82.000.000	Open to people 13 and older
orkut	Owned by Google. Popular in Brazil and India.	67.000.000	Open (Google login)
Facebook	General. Popular in Canada, UK and USA.	58.000.000	Open to people 13 and older.
Friendster	General	50.000.000	Open
hi5	General. Latin American and Asian teens.	50.000.000	Open
LinkedIn	Business	17.000.000	Open
Plaxo	Business	15.000.000	Open
Badoo	General, Popular in Europe	12.500.000	Open to people 18 and over
XING	Business	4.000.000	Open
MiGente.com	Latinos	3.600.000	Open