It looks like Facebook is now blocking a Google Chrome extension (Facebook Friend Exporter) that lets you export your data contact out of Facebook to Google Contacts or CSV. As reported by ZDNet, should one view a friend's page five times in quick succession, the email field is removed. Although the extension isn't developed for the recently announced Google+ (the extension was released way back in November 2010), its use did increase by a lot in the past week as beta users of Google+ looked for ways to port their Facebook friends to Google+.
But as pointed out in the article, Facebook is entitled to do so since Facebook Friend Exporter technically violates Facebook's Terms of Service (ToS). Section 3.2 of the ToS states:
You will not collect users’ content or information, or otherwise access Facebook, using automated means (such as harvesting bots, robots, spiders, or scrapers) without our permission.
Despite that, the creator of Facebook Friend Exporter, Mohamed Mansour, is very angry. On his Google+ profile, he wrote:
No worries, a new version is on the making ... I am bloody annoyed now, because this proves Facebook owns every users data on Facebook. You don't own anything! If I were you, I would riot this to the media outlets again.
To know more and to find a workaround to use the extension, click the source link below.