Facebook trumpets success of 'Like' buttons

The 'Like' button plug-in recently introduced by Facebook is proving an early hit on the internet, and is already installed on more than 50,000 sites, according to the social networking site.

However, the figure falls well short of Facebook chief executive Mark Zuckerberg's estimates of a billion 'Like' buttons in the first 24 hours.

The facility was launched last week at the firm's F8 event in the US, and Facebook has described itself as "thrilled" with the rapid adoption.

Facebook claims that the move will have a positive effect on advertising and marketing, but the company has received strong criticism about the possible impact on privacy.

"At F8, we launched new tools called social plug-ins, including the Like button, Activity Feed and Recommendations, on more than 75 web sites," wrote Sandra Liu Huang, a product marketing manager on the Facebook Developer Network team, in a blog post.

"We are thrilled by the strong adoption so far as developers realise how easy social plug-ins are to use, and how powerful they are in engaging users in a frictionless experience without requiring them to share any personal information."