A common mistake that many advertisers make is that they think that all social networks are the same. That the ad campaign they have for Facebook will work on MySpace, Twitter and LinkedIn.
The problem with that approach is that social networkers utilize these sites in different ways depending on their age. So one blanket campaign across the different networks is not effective.
For example, according to Anderson Analytics, Generation Z (13-to-14-year-old) social network users were more likely to use MySpace than Facebook. Only 9% of them used Twitter and none used LinkedIn.
If you want to target Generation Y users, then usage is a little different. Three-quarters of 15-to-29-year-olds used MySpace, 65% used Facebook, 14% used Twitter and 9% used LinkedIn.
For Generation X users (30-to-44-year-olds) and baby boomers (44-to-65-year-olds), they are connected on LinkedIn more than any demographic.
Nine in 10 older social network users, which Anderson Analytics called the WWII generation, use Facebook but only 17% of these users tweet.
lol 
Interesting blog, but it’s missing an important part of the equation: Generation Jones (born 1954-1965, between the Boomers and Generation X). Google Generation Jones, and you’ll see it’s gotten a ton of media attention, and many top commentators from many top publications and networks (Washington Post, Time magazine, NBC, Newsweek, ABC, etc.) now specifically use this term. In fact, the Associated Press’ annual Trend Report forecast the Rise of Generation Jones as the #1 trend of 2009. Here’s a page with a good overview of recent media interest in GenJones: http://generationjones.com/2009latest.html
It is important to distinguish between the post-WWII demographic boom in births vs. the cultural generations born during that era. Generations are a function of the common formative experiences of its members, not the fertility rates of its parents. Many experts now believe it breaks down more or less this way:
DEMOGRAPHIC boom in babies: 1946-1964
Baby Boom GENERATION: 1942-1953
Generation Jones: 1954-1965
Generation X: 1966-1978
Here is an op-ed about GenJones as the new generation of leadership in USA TODAY:
http://www.usatoday.com/printedition/news/20090127/column27_st.art.htm