Google, Facebook rivalry is getting fierce. Recently, Google  blocked Facebook access to the GMail contacts API. The company said that it would no longer let other Web services, including Facebook, to automatically import its users' email contact data for their own purposes, unless the information flows both ways.

Google accused Facebook in particular of siphoning up Google contact data, without allowing for the automatic import and export of Facebook users' information.

Facebook retaliated with a new method to get GMail contacts of an user. A Facebook engineer posted a blog comment suggesting a work-around for Facebook users to help avoid Google block.

And, Google has once again hit back at Facebook. Now when a Facebook user clicks on the Download Your Contacts button on the Facebook import contact via GMail page, he is redirected to a new page on Google's server, which has the following warning:

"Hold on a second. Are you super sure you want to import your contact information for your friends into a service that won't let you get it out?

Here's the not-so-fine print. You have been directed to this page from a site that doesn't allow you to re-export your data to other services, essentially locking up your contact data about your friends. So once you import your data there, you won't be able to get it out. We think this is an important thing for you to know before you import your data there. Although we strongly disagree with this data protectionism, the choice is yours. Because, after all, you should have control over your data."

Google then asks the user to file a complaint against this data protectionism and goes on to allow him to download his contacts.