In what is going to certainly be the next level in the fight between Facebook and Google over data portability and reciprocity, a Facebook has blocked the functioning of a Chrome browser extension that became abruptly popular after the launch of Google+. The extension, Facebook Friend Exporter, written by an open source software engineer, Mohamed Mansour, is designed to allow users to pull information about their friends out of Facebook so that they can export them elsewhere.

An update appeared Monday July 4 and a warning from Mansour about the unexpected change to Facebook over the weekend,

CRITICAL UPDATE:

Facebook is trying so hard to not allow you to export your friends. They started to remove emails of your friends from your profile by today July 5th 2011. It will no longer work for many people.

New version with a different design is currently deploying. You might have to do exports daily. It uses a different approach, and I will maintain this version. Just bear with me.

While the extension wasn’t designed to work specifically with Google+ it has seen a sudden surge in popularity with the unveiling of the service, ostensively due to the fact that the expectations for Google’s new social app are huge. In fact, the extension is currently showing 22,092 weekly installs currently with 22,414 users—meaning it probably became explosively trendy on the advent of Google+.

Emil Protalinski of ZDNet contacted Mansour to ask how Facebook had affected his software.

“Mansour says that Facebook removed emails from their mobile site,” writes Protalinski, “which were critical to the original design of his extension. He told me that the company had implemented a throttling mechanism: if you visit any friend page five times in a short period of time, the email field is removed.

“‘Facebook is actually hiding data (email) from you to see when your friends explicitly shared that to you,’ Mansour told me in an e-mail. ‘Making it really hard to scrape because the only missing data is your emails, and that is your friends identity. Nothing else is.’”

It’s been pointed out by others that Mansour’s extension is a prima facie violation of Facebook’s terms of service forbidding the use of software or mechanistic scrapers to grab information from their pages without permission. Facebook even blocks the GoogleBot search engine spider from their pages with robots.txt. In fact, it is a long standing struggle between Google and Facebook to get the social network to release any information (even publicly available) to its users without a tussle.

For Facebook, this may actually be less about Google and more about them reacting to what they see as a sudden issue with the privacy of their users—although they probably get that it must be related to Google+. Facebook will probably spin this as protecting their users’ privacy when they’re finally called to the mat. However, as we all know, Facebook has already been caught with their hand in the “Be Evil” cookie jar once before involving hiring a publicity firm to make up negative press about Google+ long before it even arrived on the scene.

This isn’t over.