For example, if you were to log in to Twitter via your MySpace credentials, Twitter could then scan your MySpace friend networks and find those same people on Twitter. You wouldn’t need to worry about knowing their Twitter usernames, since the connection would already be established through MySpace.

Another interesting part of MySpace’s plan is that the third-party sites using the new tools are not allowed to store any of your data.

On one hand, the no storage policy gives you more control over where your data ends up. It ensures that if you share your MySpace data with another site, but then change your mind and decide to stop sharing it, that data will instantly disappear from the outside site. However, it also means that your data is ultimately still stuck on MySpace.

While MySpace’s new features cover about half of the goals outlined by the Data Portability Workgroup (which MySpace joined Thursday), it doesn’t offer true portability. One the bright side MySpace seems aware of the difference. The company is even using the term Data Availability rather than Data Portability.

What’s the difference? Well, think of your personal data as your life savings. MySpace’s new tools are an ATM card. Sites using the new tools are like ATM machines and you can have access to your cash from just about anywhere and enjoy using it all over the web.

However, you still can’t withdraw all your money and put it in another bank.

True data portability would mean having an ATM card that works everywhere, and allows you to move your money to another bank account without having to get a new ATM card. In other words, where the actual data resides should be irrelevant, but it’s not. Yet.

A broader vision of data portability would mean you could use MySpace as a host for your personal data and then one day decide you want to hand that duty over to Facebook. In such an ideal world, all you would need to do is login to Facebook, sync your MySpace data over and then disallow MySpace any future access to that data.

For now, that remains a difficult and ephemeral goal.

There are two basic problems with the data portability scenario. First, no site -- MySpace, Facebook or anyone else -- wants to make it that easy for you to turn your back on it. So, there’s very little incentive for them to embrace a plan like that. The second problem is how to get rid of the data on the original host when you move to another host. In other words, when you switch from MySpace to Facebook, how do you get rid of the information on MySpace’s servers?

These hang-ups make true Data Portability difficult to sort out, and there isn't going to be a complete workable solution for some time.

That said, MySpace’s announcement is big. While the site might not be the choice of the online hipster crowd, it has a massive mainstream user base. By opting for the pragmatic solution — make data available to outside sites — MySpace is effectively exposing some of the benefits of data portability to a much wider audience. Whether or not that audience gets excited about the new features remains to be seen.

For the launch, MySpace has partnered with Yahoo, eBay, Twitter and its own Photobucket service. As far as I can tell, however, the plan is to eventually make the API available to everyone. The press release isn’t clear on when the actual APIs will be publicly available, though Data Portability co-founder Ben Metcalfe says the tools will be open to everyone.

Some other key parts of MySpace’s plan remain unclear as well. For example, what sort of data formats and APIs will be used? Authentication will be handled through oAuth, an emerging standard for logging into websites, but the APIs and other tools are thus far a mystery.

In the end, the real winner in MySpace’s plan may well be Twitter. Although none of the partners have any tools developed at the moment, if Twitter implements something like the mockup seen on the right (which comes from TechCrunch -- click on it for the larger version) the service is poised to jump from a toy of the tech-savvy elite to a mainstream audience. Hopefully, Twitter’s servers are up to the challenge.

While it may not be the end-all data portability solution that some have been hoping for, turning MySpace into an ATM card for your personal data is certainly a huge step in the right direction.