As a baseball fan, reality is incomplete until it is quantified. That’s why reading Nielsen’s report of Twitter’s 2008 growth is fascinating, despite the fact that everyday we read about who or what is now tweeting. Between Septembers 2007 and 2008, Twitter’s audience grew from 533,000 to 2,359,000 users, a change of 343 percent.  It's almost three times the growth of the other site that gets as much press: Facebook.  Surprisingly, as fast as Facebook is growing, it is only the 6th fastest site.

Nielsen’s top ten fastest growing social networking sites are:

1. Twitter: 2,359,000 users; 343% growth.
2. Tagged: 3,857,000; 330%
3. Ning: 2,955,000; 251%
4. LinkedIn: 11,924; 193%
5. 1,879,000; 121%
6. Facebook: 39,003,000; 116%
7. MyYearbook: 3,056,000; 115%
8. Bebo: 2,418,000; 86%
9. Multiply: 941,000; 59%
10. Reunion: 7,601,000; 57%

In terms of audience size, Twitter is not even in the top ten. And while Facebook has eclipsed MySpace in press and word of mouth, it still only has two-thirds of MySpace’s 59,000 members. That of course is rapidly changing, and what is somewhat surprising is that MySpace membership totally plateaued this year, growing just one percent. Facebook, on the other hand, grew by 116 percent, from 18,000 to 39,000.

It is interesting that the neither of the two most-talked-about social networking sites of 2008 has the biggest audience.

MySpace continues to be the top social networking site, followed by Facebook, (17,075,000), LinkedIn (11,924,000), Windows Live Spaces (9,117,000), (7,601,000), Club Penguin (4,224,000), AOL Hometown (3,909,000), Tagged (3,857,000), and AOL Community (3,079,000).

While social networks continue to grow, monetization still remains a problem. EMarketer has just downgraded its 2009 ad-revenue projection for social networks more than a quarter from $1.8 billion to $1.3 billion.

Notable 2008 underperformers were MySpace and Facebook. It is estimated that MySpace is off 22.5% from 2008 revenue projections of $755 million, and Facebook is off 20% from its estimated $265 million 2008 revenue. Emarketer does not expect either site's 2009 revenue to match even 2008’s projections.

By Mark Alvarez