Google allows its users to download their data for exporting elsewhere. But after their tough stance against Facebook not sharing its own data, they blocked that option. Facebook's cleverly circumnavigated the block, meaning Gmail users can still find friends there.
It's a big power struggle, and one that won't end prettily. Google could try and patch up the hole which Facebook has taken advantage of, where users can download their details from Gmail and upload the file to Facebook using a direct deep link—but an engineer who spoke to TechCrunch about the tech specifics said while it's easy, it "might fuck up other CSV flows."
Whatever happens next, I'm willing to bet it's going to make for very interesting watching from the sidelines. But good luck to Gmail users who are yet to sign up to Facebook—and yet to import their contacts list over there. [TechCrunch]
UPDATE: Google got in touch with the following statement:
"We're disappointed that Facebook didn't invest their time in making it possible for their users to get their contacts out of Facebook. As passionate believers that people should be able to control the data they create, we will continue to allow our users to export their Google contacts."