Did college-age kids kick their parents off the site? Or have they fled Facebook for the latest craze, Twitter?

Hard to say. "Maybe older users are still getting acclimated to how to use Facebook's real-time stream to share information with friends and family," surmised Inside Facebook editor Justin Smith.

That view suggests the latest redesign that rolled out in March, featuring more frequent updates in users news feeds, may not have been to their liking. The changes provoked a backlash that led the social network to make revisions that give people more control over what type of information appears in their "stream."

In any case, Facebook's overall growth slowed in the last two months from the beginning of the year. In April and May, active U.S. Facebook users increased 4% to 60.4 million, compared to 11% to 56.1 million in February and March.

Growth only accelerated in the 18-to-25 age bracket, which surged by 1.8 million users and makes up one-third of all Facebook members. By contrast, the increase in users 35 and over -- which had doubled in February and March to 17.1 million -- slowed considerably in the last two months, adding only about 292,500.

Those ages 26 to 44 now make up 43% of Facebook users, however -- up slightly from the 41% at the end of March. Women still represent the majority of Facebook users at 56%, with more women than men in every age bracket.

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