YouTube was the fastest growing social network in April for the second consecutive month, according to the latest figures from Experian Hitwise.
The online video website now accounts for 1 in 5 visits to a social network from UK Internet users, up from 1 in 6 visits back in April 2010.
It is now firmly established as the third biggest website in the UK, overtaking Hotmail in December 2010.
Facebook lost market share of visits for the second consecutive month in April, dropping below the 55% market share threshold for the first time since August 2010.
Within the top 10 social network and forum websites, Twitter, Yahoo! Answers and Tumblr were among the fast climbers of the month.
Year-on-year, eight of the top 10 social networks increased their market share of clicks, as the top networks cemented their places at the top of the industry.
Notably MySpace and Club Penguin dipped in market share both month-on-month and year-on-year.
Research director Robin Goad added: "MySpace has been on the wane for some years now, and at its current rate of decline it won't be too long before it drops out of the top 10 social networks altogether.
"Not so long ago MySpace was equal to Facebook; now Facebook commands 100 times more traffic than MySpace. The social media landscape is constantly evolving, so it is important to get a heads up on which social networks are growing and which are shrinking as this can have a massive impact on the success of online marketing campaigns."
By Bev Fearis
Monday, May 9, 2011