Last week, after adding new granular privacy controls for showing or hiding email addresses you've listed, Facebook hid every email address you've ever added to your profile. Since your @facebook.com email address is the same as your Facebook.com URL (which anybody can see), Facebook didn't bother hiding that address. It ended up seeming like Facebook forced its own email service on users, when in reality, it just made a mistake in executing a new privacy initiative.

The point was to give every user a fresh start in showing or hiding email addresses they've added to their profile. The goal was to let everybody start from scratch, a Facebook spokesperson told us, but the repercussions of the company's actions are likely more far-reaching than it could've foreseen. ReadWriteWeb today pointed out that those with Facebook contact sync enabled (many Android, Blackberry, and iOS 6 beta users) have lost valuable email addresses inside their phone's address book. It makes sense that this would happen, since Facebook contact sync only syncs visible email addresses associated with a friends' profile. While it's a simple matter of just unhiding email addresses you want friends to see, Facebook pushes out updates nearly every day and most users are confused as to what happened.

Most people wouldn't email a friend at their @facebook.com email address, but many are finding themselves without a choice. Facebook contact sync occurs in the background, so many people thus far have sent emails to friends without realizing that the friends' email address had changed in their phone's address book. These emails likely end up in the recipients' "Other Messages" folder, a dark place generally reserved for spam and misery. Most people probably aren't even aware that the Other Messages folder exists, let alone have checked it.

It's unlikely that the company will undo its actions to hide all of your email addresses by default, so everyone will need to unhide email addresses manually. To unhide your email addresses, click "About" underneath your profile picture, then click "Edit" in the Contact Info box. From there, click the drop-down menu next to an email address to edit its visibility.

Until everybody unhides their primary email addresses, those relying on Facebook contact sync for email will be left without a lot of information they're used to having stored on their phone. Of course, email addresses you've manually added to a friends' contact card on your phone will be unaffected, and perhaps that's the lesson here. While at some point down the line, your phone's address book will auto-update whenever your friends change phone numbers or email addresses (pioneered by WebOS' synergy feature), we're not quite there yet.

Update: We've spoken to Andrew Bosworth, Facebook's Director of Engineering, who responded to the email address and contact sync issues.