Emails sent to the Facebook address end up in the site's messaging system, rather than users' email accounts. Photograph: Karen Bleier/AFP/Getty Images
Facebook has introduced its latest social media innovation – changing the email addresses posted by users on their profiles, en masse and without warning.
In the change, which took effect on Monday, Facebook abruptly replaced the details users had elected to associate with their account with addresses using a "@facebook.com" convention.
Emails sent to the Facebook address end up in the site's messaging system, rather than users' email accounts.
Facebook allocated users an email address based on their profile URL, if they had elected to choose one. Users without a customized URL were instead issued with an email based on their profile name, with the addition of a few numbers.
The new contact details were automatically displayed on users' timelines, while the old email addresses were hidden. Users have to go through a number of stages to restore the previous details. Facebook has made no announcement to users about the changes, nor explained how to reverse them.