The promise of data portability may still be a long way off, but the war to control how users move their data from one site to the next appears to be well underway.

After last week's news from MySpace and Facebook that each had launched competing data portability products, Google has come out with something called "Friend Connect."

At their core, each product purports to do much the same thing -- let users share their data with any publisher or community that adopts the MySpace, Facebook or Google protocols. But the trouble is that interoperability -- the key to data portability -- will likely be hindered by competing platforms. However, that picture is somewhat muddled by the fact that Friend Connect will dovetail with Google's Open Social, another data portability initiative run by Google that has the support of MySpace.

According to a TechCrunch report, Google's Friend Connect may differ slightly from projects launched by MySpace and Facebook insofar as the search giant appears to put tighter restrictions on how third-party publishers can use the data.

Although it may be too early to tell which company will ultimately carry the day (MySpace with a wide range of partners appears to be in the lead), the stakes are clear. The successful company will become something of a clearing house for user data and serve as a de facto hub where people can update personal information and apply changes instantaneously across the web.