Facebook to target ads based on users' trail

David Gelles:

Facebook has laid the ground for a new system that would track its users' behaviour as they visit other sites around the internet, using the information to deliver highly targeted advertisements to them on the social networking site.

So-called "behavioural targeting" is widely used by companies such as Google but, on Facebook.com, the move is likely to provoke a new round of criticism over incursions into users' privacy.

In order to make the system work, Facebook is planning to unveil this week a content-sharing button that other websites can embed on their pages, according to marketers briefed on the plans. Similar to buttons from Twitter and Digg that let users share content with their social networks, the Facebook button will allow users to signal the content they like on sites around the internet.

However, data from these interactions would be used to target them with related adverts once they return to Facebook.com