Traffic to social bookmarking site Del.icio.us has doubled since it was acquired by Yahoo in December last year.

According to figures released by web monitoring firm Hitwise, from a sample of 10 million US internet users, visits to Del.icio.us increased 122 per cent from January to July this year.

Despite the huge increase, Hitwise noted that Del.icio.us still only ranks 6,793 among all sites visited. Social bookmarking still has someway to go before hitting the mainstream, the company said.

The site is particularly popular among males aged 25-34. For four weeks up to 5 August 2006, 59 per cent of visitors were male and four out of 10 were aged 25-34.

Del.icio.us also attracts a fair share of moneyed surfers – over a third of its visitors fell into the $100,000 to $150,000 a year household income bracket, compared to just 13 per cent for the overall online population.

"Del.icio.us is highly skewed toward the social groups U1, 'Urban Uptown', and S1, 'Elite Suburbs'," said LeeAnn Prescott, senior research analyst at Hitwise.

"Members of these social groups have higher than average incomes and tend to be highly educated and are more likely to be early adopters of technology.

"My guess is that they've heard about Del.icio.us through news media or through friends and are using it because it's 'the thing to do'.

"This is not quite the MySpace crowd that I expected to find – intead Del.icio.us users are a more sophisticated breed of web power user."