Upon researching, I found the following posted in Google Answers:
"...
Friendster used viral marketing to grow its user base. In less than 6
months it had approximately 1.8 million users with almost no marketing
budget.
http://www.loiclemeur.com/english/2003/11/the_dating_indu.html
..."

I have a shoppping portal that pays cash back to members based on
their purchase amounts.  The site is free to join and members can shop
at over 500 retailers.  I'm interested to know 'specifically' what
Friendster did to gain this many members so fast.  What viral marketing
methods did they conduct, what companies did they work with, where can
I find the creative (if possible),
and what other tactics did they do.  I too have limited marketing
funds and am interested in any other success stories on membership
acquisitions with specific details.

"Viral" is not a good thing.  I went from getting zero spam on my work
e-mail to around 30 spams a day after my roommate/friend/hag
registered me on friendster with my work e-mail address.