'About 20 percent of people between the ages of 18 and 34 have used a status-updating service, the research found (considering Facebook's ubiquity, this actually is lower than I would have expected). Then it starts to drop off. Only 10 percent of those between 35 and 44 answered affirmatively, 5 percent of those between 45 and 54, 4 percent between 55 and 64, and only 2 percent of those over 65. Okay, not surprising.

There were a few tidbits about individual social-networking sites. The average Twitter user, the study found, is older than a Facebook or MySpace user: 31, compared to 27 for MySpace and 26 for Facebook. (The average user of professional networking site LinkedIn is 40, according to the same Pew data.) Well, that's kind of interesting.

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