Pew Charitable Trust report by Eulynn Shiu and Amanda Lenhart on How Americans Use Instant Messaging has been released. Some findings:

Although most internet users favor email over IM as a form of communication, nearly a quarter of IM users say they instant message more than they email [emphasis mine]:

• 24% of those 54 million IM users report using IM more frequently than email and 6% of IM users say they use IM as much as they use email.
  
• 70% report using email more than instant messaging.
  
• 36% of IM users say they use IM every day and 63% say they use IM at least several times a week.

Within the instant messaging Gen Y (18-27 years) age group, 46% report using IM more
frequently than email. In contrast, only 18% of Gen X-ers (28-39 years) instant message more often than emailing. In older generations the percentage is even smaller.

• 21% of IM-ers in each of the Gen Y and Gen X age groups log onto IM several times a day, followed by 17% of Trailing Boomers (40-49), 15% of Leading Boomers (50-59), 10% of Matures (60-68), and a mere 9% of the After Work (69 and older) age group.
  
• 35%, or the largest portion of those who IM for about an hour are Gen Y-ers. In contrast, the greatest percentage of instant messengers who IM for less than 15 minutes consist of Trailing Boomers (26%).

I found other demographics interesting, as well: that women IM more than men, and lower income people IM more than those with higher income. Personally, I interpret that with the natural conservativism of older, more well-educated, and more well-off people, who tend to stick with established communication media out of a sense of formality and perceived rightness. IM does tend toward the informal and spontaneous, and has dropped a lot of the ancient letter-writing style that still pervades email, with the antiquated "Dear Mr. Jones" and "Sincerely," and so on.

On the other hand, IM is a conversational medium, and a lot of the old etiquette folderol is just not there at all, and its hard to push it back in. It would be nearly impossible to IM someone saying, "Dear Mrs. McGillicuddy, How are you today?" No, the more typical "hi, what's up" exemplifies the split between IM and email.

I find that the extensive IM that I am doing these days is leading to a more IM-ish style of email, where I am not starting messages with the recipient's name (they know who they are, don't they, and its in the To: field already) and I am likewise dropping the 'best wishes - Stowe' at the end, for similar reasons. I am increasingly using email (when I use it) as very slow IM, rather than thinking of IM as very fast email.

[Pointer from Kevin Philbin]