SAN FRANCISCO: Twitter is the fastest-growing "member community" site in the US, posting an uplift in user numbers of 1,382% for the year to February 2009, meaning it was well ahead of more established rivals including Facebook on this measure.

The rise of Twitter was argued to be one of the main features of the digital media landscape last year, and looks set to continue in 2009.

According to Nielsen, over 7 million Americans visited Twitter in February 2009, compared with a total of just 475,000 in the year-ago period.

In terms of overall growth, Zimbio, a social media site billing itself as an "interactive magazine", took second place, with its number of unique users in the US rising by 240% from 809,000 to 2.8 million.

Facebook was in third spot overall, with an improvement of 228%, but dominates in terms user numbers, which rose from 20 million in February 2008 to 66 million a year later.

In fourth position was Multiply, the blog, video, photo and music-sharing portal, which recently bought MSN Groups from Microsoft, and has increased its user base from 821,000 to 2.4 million over the course of a year, an uplift of 192%.

Wikia, a community site that allows people to create and edit content on any topic, made up the top five, having boosted its user numbers by 172% for the year to February, from 1.4 million to 3.8 million.

Data sourced from CNET; additional content by WARC staff