Not cool Facebook; no, not cool.

As if it wasn't enough that the social networking giant had forced @facebook.com e-mail addresses on all its users earlier this week, now users are reporting that their address books are being altered, and e-mails are being lost.

Violet Blue over on c|net is reporting that Facebook users say contacts' e-mail addresses on phones and personal devices have been altered without their consent -- and their e-mail communication is being redirected elsewhere, and lost.

Rachel Luxemburg, an employee of Adobe has reason to be angry, she writes:

Today, a co-worker discovered that his contact info for me had been silently updated to overwrite my work e-mail address with my Facebook e-mail address. He discovered this only after sending work e-mails to the wrong address. And even worse, the e-mails are not actually in my Facebook messages. I checked. They've vanished into the ether. For all I know, I could be missing a lot more e-mails from friends, colleagues, or family members, and never even know it.

Luxemburg adds that despite quickly changing the @facebook e-mail back to the correct e-mail address once she found out about Facebook's change, it's still happening.

When the change was forced through, valid email addresses began to update on address books of phones and computers of other contacts outside of Facebook without the users' awareness or consent.

The horror stories aren't limited either as several other websites have pointed out. For now our best advice is to check your contacts if you sync contact information with Facebook, right now.

Users who wish to reinstate their actual email addresses on their Facebook profile pages can follow these steps: On your profile page, click About, scroll down to the "Contact Info" box and click the Edit button. Hide the @facebook.com email address from your Timeline and replace it with one of your real email addresses.

Update: The email address listed in your "Account Settings" isn't the one that was changed, as other people are assuming. It's the contact email address in your timeline: About > Contact Info section. You will notice that only your @facebook.com email address is visible, others are set to hidden from timeline. An example of this can be seen in the image at the top of this article.

Source: C|net