Facebook is trying to force its 900million users to switch to its own email service.
It is removing the personal email address displayed on an individual user's profile pages and replacing it with a @facebook.com address even if the member never uses it.
The social networking site's email service was launched two years ago but has failed to take off, possibly because most people do not like having multiple mail accounts.
Facebook users who were not consulted about the move responded with anger. Blogger Gervase Markham, one of the first to notice the change, said it was a form of computer hacking. 'What on earth do they think they are playing at?' he said.
On Twitter, Facebook was branded 'sneaky' while CNN technology expert Julianne Pepitone claimed it was an attempt to 'hijack your email address'.