The Data Portability wars just got a little more interesting. Power.com, the service that lets users aggregate their social networks into a single hub, is countersuing Facebook for restricting users’ ability to export and move their own data. The company is claiming that Facebook is unlawfully withholding the data that users own (as stated in Facebook’s own ToS), and is stifling competition by refusing to allow third party services like Power.com to access the data, among other things. This should be fun.

It’s been over six months since we last heard about these two duking it out, so here’s a quick refresher: Power.com launched last August, offering users the ability to import their latest updates and user information from Facebook, MySpace, and a number of other social networks. It did so by tapping into the social networks’ APIs when available, but also by scraping user data when they couldn’t access it through other means — a big no-no for most social networks, as we saw with the Scoble/Plaxo fiasco. It didn’t take long for Facebook to file suit against Power.com for scraping user data and storing user credentials (another violation of Facebook’s ToS). A week later we heard that the two parties might be close to a settlement, but apparently that didn’t work out — the suit is still pending.

Power.com CEO Steve Vachani likens the current situation with Facebook to one the cell phone carriers saw before they allowed for number portability. In the case of the cell phones, users were effectively locked into a certain carrier because they had spent so much time building up contacts and giving them their phone numbers, and it would be too much effort to switch to a new one. It’s an analogy that has been drawn since the data portability movement began, and while it may make sense, there’s no guarantee the courts will view phone numbers and a user’s social network data in the same light.

That said, Power.com is making some good points. The idea that users aren’t allowed to input their username and passwords into other services is particularly hypocritical, as that’s exactly what Facebook invites you to do to import contacts from services like Gmail and Yahoo Mail.

Facebook can point to its efforts with Facebook Connect, which lets you log in with your Facebook username at third party sites and import some select data from your profile, as evidence of its openness. But this isn’t true data portability, it’s just a new walled garden — third parties are generally only allowed to cache your data, which means that you’re still tethered to Facebook.

Of course, while we may not like the current situation, there may well not be anything illegal about it — that’s up to the courts to decide. We’ve all agreed to the Facebook Terms of Service, and there’s no question that Power.com breaks them. We’ll be following the upcoming case closely.