Twitter users tend to be older than other social media users

"Twitter users tend to be older than non-Twitter social media users (54% over 30 years old, vs. 42%), twice as likely to be self-employed or entrepreneurs (18% vs. 9%) and to be planning to start a business during the next six months, and more tech-savvy (24% vs. 15% "buy gadgets/devices when they first come out," 48% vs. 30% have created a website, and nearly four of ten (37%) currently maintain a blog, twice as many as non-Twitter social media users)."
Source: Crowdscience, 22nd September 2009
Other twitter stats also contained in the article