A quarter of all US surfers now regularly visit social networking sites, according to statistics released by the Consumer Internet Barometer.
Around half of these visit sites such as Facebook and MySpace on a daily basis, and a quarter log-on several times a day.
Among household members those aged 12 to 17 are more likely to be daily users, and 57 per cent say that they visit social networking sites at least once a day.
The Consumer Internet Barometer is based on a quarterly survey of 10,000 households and is produced by The Conference Board, a global business research and membership organisation.
"Online social networking is an integral part of many people's lives and a natural extension of our means of communication which the internet has created, " said Lynn Franco, director of the Conference Board Consumer Research Center.
"The next growth wave will be expanding and incorporating these networks into our business lives."
Four out of five online consumers cited 'connecting with friends' as the number-one reason for visiting social networking sites.
About half of all users reported using sites like MySpace and Facebook to update and maintain their online profile, send email and connect with family.
At least one in five social network users logs on to blog or meet new people. Among the 30 and over working-age population, one in eight uses social networking sites to conduct business.
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