With iOS 6, your iPhone address book may be invaded by Facebook email addresses

I'm generally a fan of Facebook. I only use it to keep in contact with people I actually know and hang out with in real life. And for my friends that live in other countries, it's the easiest way to share photos, videos, and other life events.

That's why I'm pretty excited about the iPhone's Facebook integration in iOS 6. The ability to post to Facebook from almost anywhere in iOS, use single sign-in to log into any number of apps, and 'like' apps and songs is going to be great. However, there's one unpleasant outcome of Facebook integration in iOS 6: it may load up your contacts list with loads of practically useless @facebook.com email addresses. As I'll explain, this is a huge boon to Facebook's underutilized email service, but a bane to iOS users (and within a matter of days, OS X, Windows, and Android users) across the globe.

First the good news: In iOS 6 (and OS X 10.8.2) Apple and Facebook have teamed up to sync your Facebook contacts and their info with the contacts in your existing Contacts app. This is actually a win for users, because most people update their mailing addresses, phone numbers, instant messaging names, and emails addresses on Facebook more often than they would manually send out vCard or simple email updates to contact details. The Facebook contacts sync, in the end, automatically updates your friends' info in your Contacts without you (or your friends) lifting a finger.

Syncing contact info is an all-or-nothing feature.

Now for the bad news: iOS 6's sync options may also be a Trojan Horse for Facebook's underwhelming email address service. Since 2010 Facebook has offered all of its users @facebook.com email addresses based on the Facebook vanity URL name on the account (the words that appear after the www.facebook.com/ in your Facebook profile's URL). And if you haven't chosen a vanity URL, it's a lot worse: you'll be assigned an @facebook.com email with random numbers in front of the @, à la CompuServe in 1994. Any email sent to your Facebook email address will be automatically routed to your Facebook messages folder on Facebook.com.

With the rollout of @facebook.com emails in 2010, Facebook aimed to take on Gmail and improve the stickiness of Facebook.com. That way, when you checked your email you'd be going to Facebook instead of Google or Yahoo or AOL. But as Facebook discovered, no one really cared (or knew) about their @facebook.com email addresses. That's why in June of this year, without notifying users or getting permission, Facebook set every single Facebook user's publicly listed profile email to their @facebook.com email address and hid all their other email addresses from view. Facebook's excuse for this was that they were protecting user privacy, but that's pretty much total crap.

It got worse in July, as early beta testers of Facebook sync discovered quickly that the @facebook.com addresses were replacing the default addresses for scores of contacts. The sync API was pushing the most-recently-added email address, rather than the primary -- which automatically meant the @facebook address, since that was newest. While this behavior was deemed to be a bug by Facebook affecting "certain devices" and quickly fixed, our tests now show that the @facebook addresses are still being sync'ed over alongside the user's real world, primary email address.

Here's the big problem: Most of Facebook's 900 million plus users still don't know @facebook.com emails exist, yet their @facebook.com email is now listed on their profile by default -- unless they've gone in to change settings to hide the (useless) email address.

So what's going to happen in 2-3 weeks when iOS 6 comes out? There are 900 million Facebook users. There are going to be close to 400 million iOS 6-capable devices in the wild by the end of this year. If even a quarter of those users enable Facebook contacts sync, we could have scores of @facebook.com email addresses added to 100 million users' contact lists.

As an Apple user who likes clean, uncluttered interfaces, this is a huge drawback. Suddenly all of my contacts will now have at least two email addresses (their "real" one and their unused @facebook.com one). That means when I start typing their name in Mail's "To" field I'm now going to have to select from at least two choices for their email address -- or even more if they already have multiple emails. The result? More taps and impaired productivity.

Yes, after I select the primary email address enough times, eventually it will default to the top of the list, but most email users aren't as tech savvy as the people reading this and they might not even notice the "@facebook.com" email address they're using to send their friend a message. And it's not like anyone ever goes to Facebook to check emails when someone says "Didn't you get that email I sent you?" so the result could be a lot of misdirected messages.

Useless contact detail is never good for an OS that prides itself on simplicity.

But this isn't just a complaint about data clutter and user confusion. Yes, the Facebook contacts integration is only on iOS and OS X, but the Contacts apps on both of those systems sync to other email services (like Gmail, Outlook, etc) and Windows PCs, which then connect to Windows Phones and Android phones and all their contact books and Exchange servers and the list goes on and on. (There are already Android phones that sync Facebook contacts, as well as plenty of third-party apps that enable sync.) So it's entirely possible that within 48 hours of iOS 6 launching, Facebook will have successfully spread its @facebook.com email address to many millions of contact books and email clients -- on myriad types of devices -- across the globe.

That's something Facebook has never been able to do with the @facebook.com email addresses, until now. It's of a piece with the shady default "public" email change they made for users a few months ago (which I'm sure, "coincidentally" for them, timed nicely with the upcoming iOS Contacts sync).

It's sneaky, and in my opinion it's wrong. While no one at Facebook would send me an email saying "Yeah, this is something that's gonna work really well for @facebook.com email adoption," I've spoken to plenty of Facebook employees off the record. They say Facebook isn't exactly unaware of the benefits iOS sync will deliver to Facebook's email rollout.

So what can you, the user do? As a symbolic protest, you can hide your @facebook.com email address from your Facebook friends. This won't stop it from being synced with your Contacts on iOS and OS X, but it will keep Facebook friends from picking it up off your profile page. If you want to make sure it doesn't sync out to other people's address books, commenter Chris suggests setting the Privacy flag on the @facebook address to "Only Me" -- that will keep it entirely secret and out of everyone's hair. To make either of these changes, click the Update Info button on your profile page, then scroll down to Contact Info on the right and click Edit. Find your @facebook address and then set both flags to maximum privacy.

Once iOS 6 and OS X 10.8.2 arrive, you probably will want to wait a week or two before enabling Facebook contact/calendar sync, to give this whole mess a chance to sort itself out. But what if there turns out to be no way to block the @facebook.com address invasion? That would be a shame because, besides the @facebook.com email mess, the Facebook integration is going to make a lot of things easier for iOS and Mac users. Other than that? Hope Apple adds selective sync to allow you to control which information iOS draws from Facebook to add to your Contacts.

As I've said, this is not only something that will affect iOS or Mac users. The @facebook.com emails will use iOS and OS X as a Trojan Horse and ride it into contact books and email servers across devices across the globe. And that wouldn't be a bad thing if people wanted to use their Facebook email addresses as their primary ones or even as a secondary option, but given that @facebook.com email adoption is basically nill after two years, I'm going out on a limb and saying no one really wants it. It's just excess data that we have to sift through and it shouldn't be forced on us in the guise of otherwise excellent new features.