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The battle over who controls the information in your social graph — and specifically, who controls the email addresses of your contacts — continues to ramp up. Just a week after shutting down a Chrome extension that let you pull that information out of Facebook, the social network has flipped the kill switch on another service from Open-Xchange that provided a similar export capability. Although the company says its service abided by all the terms of the Facebook public API, it has become the latest victim of Facebook’s ongoing attempts to maintain control over the contact info of its users.

The shutdown of Open-Xchange’s address-book-exporting service makes the issue even more obvious, since it’s a more straightforward offering than the Chrome extension developed by Mohamed Mansour. The programmer launched the extension last fall as a way of allowing users to move their contacts out of Facebook, after Google changed the terms of its API in order to highlight the social network’s refusal to allow users to export that data. But Mansour’s solution effectively just scraped the Facebook site — rather than using the approved API to access the data — and that’s expressly forbidden by the company, making it easier to justify the shutdown of the service.

Open-Xchange’s service, however, isn’t a scraper at all. It uses the social network’s approved API, and according to a press release from the company — which makes an open-source email server and collaboration system — it obeyed all the various restrictions that Facebook places on dealing with user data. According to an email from Facebook sent to the German company, however, the address book application was disabled because it allowed users to export email addresses of their contacts without the approval of each of those users. The Facebook email said:

You cannot use a user’s friend list outside of your application, even if a user consents to such use, but you can use connections between users who have both connected to your application.

In other words, in order to behave the way that Open-Xchange intended — by allowing users to import and consolidate their address books from different services and social networks — the German company’s service would have to require that everyone in a user’s Facebook contact list also join the service and authorize the export of that information. In the company’s news release, Open-Xchange CEO Rafael Laguna railed against Facebook’s control over a user’s data, saying:

If you want to see what a future looks like where a single company controls YOUR personal data for its own profit, this is a glimpse. Clearly, Facebook management does not want you to have the ability to take your personal information outside their walls to, say, Google+ and will do everything in their power to stop you, including violating their own terms and conditions.

We’ve reached out to Facebook for a comment and will update this post if we get one, but what the social network’s behavior in this case — and the case of the Chrome extension — makes clear is that the company believes it needs the approval of each user before it allows anyone to export their email addresses. As we noted in our post about the Chrome extension, Facebook executives have repeatedly said that they believe each user owns their email and other contact information, and that while it might be okay for email programs such as Gmail to allow export of those addresses, Facebook doesn’t believe that it should do this — and some supporters, including media analyst and author Jeff Jarvis, agree that they should not provide this info for privacy-related reasons.

What Facebook still hasn’t explained, however, is that users can easily export all of the email addresses and other information from their contacts by using a Yahoo (s yhoo) email account. In fact, the Yahoo importer allows you to use Facebook Connect, so the whole process takes about three clicks. And iPhone (s aapl) users can also import and sync all of the Facebook data for their contacts, creating a single unified address book — in other words, exactly the same thing that Open-Xchange was trying to provide. Why are these other methods allowed when the Germany company’s export feature is blocked? That isn’t clear.

What is clear is that Facebook sees that contact information as a crucial resource that it needs to maintain control over, either because it doesn’t want to give new networks such as Google+ a leg up in gaining new users, or because it foresees some kind of privacy backlash if it allows widespread export of users’ email addresses. But Google — which has launched a full-fledged data export tool called Google Takeout, the product of an internal team called the Data Liberation Front — is unlikely to give up the fight.

Which raises the question: Do you mind if a user that you are connected to through Facebook exports your email address to use in another service such as Google+? Let us know in the comments.

Post and thumbnail photos courtesy of Flickr user Rupert Ganzer