Thanks for Social Media Today for this http://www.socialmediatoday.com/SMC/78505 great to know this.

PEW survey of usage on twitter or twitter-like service for online adults - 2253 interviews conducted Nov-Dec 2008, of the total 2253, 1650 were Internet users. 502 interviews were by cell phone which is new by the way, since until recently, surveys used to avoid reaching people bycell phones. They caved when they found they could not get good results because more and more people are only reachable by cell phones.

Source http://www.pewinternet.org/pdfs/PIP%20Twitter%20Memo%20FINAL.pdf

Be there or be square: or can it be true, 3% of internet users twitter?

PEW says 27% of bloggers twitter - this says that the "influencers" are on twitter the most, by my read, since only 13% of internet users blog. (27% of 13% is about 3% and a bit)

Keeping up with the blogosphers:
21% of twitter users read a blog "yesterday"

* 19% age 18-24
* 20% age 25-34
* 10% age 35-44
* 5% age 45-54
* 4% age 55-64
* 2% age 65+

And thinking of households shared by students, yep, they probably beef up the stats here

* 17% in households earning less than $30,000 tweet
* 10% in households earning more than $75,000 tweet

Comparison of media age of social media users

Linked-In user is 40
Twitter user is 31
Myspace user is 27
Facebook user is 26