The industry momentum for data portability brotherhood hit a bump on Thursday when Facebook blocked Google's Friend Connect service from accessing Facebook members' data.

Friend Connect violates Facebook's terms of service because it "redistributes user information from Facebook to other developers without users' knowledge," Facebook official Charlie Cheever wrote on the company's blog for developers.

"Just as we've been forced to do for other applications that redistribute data in a way users might not expect or understand, we've had to suspend Friend Connect's access to Facebook user information until it comes into compliance," Cheever wrote.

Facebook has already contacted Google "several times" about the issue and is looking forward to finding a resolution, according to Cheever.

Friend Connect, Facebook Connect and MySpace Data Availability are separate initiatives announced in the past week designed to let people reuse the content from their social network profiles in other sites.

The main idea behind this data portability concept is to save people from having to reenter into multiple sites common profile information like their personal interests, list of friends, photos, video clips, blog postings and the like.

However, none of the three initiatives even comes close to providing a broad data portability solution, although MySpace, Google and Facebook have been commended by industry observers for at least taking some first steps to address the issue.

It's not a secret that data portability itself is a complicated matter to solve due to significant technical as well as commercial and operational challenges that surround it.

Thursday's move by Facebook highlights just one of the considerable obstacles for data portability: the different user-privacy policies and settings that exist among social networks and online service providers. These policies and settings need to be reconciled and harmonized in order for them to share and accept user data from each other.

Google didn't immediately respond to a request for comment about Facebook's decision to block Friend Connect.