Facebook, which is quite a hit on smartphones such as Apple’s iPhone, is making a debut on Sony Ericsson’s Xperia X1 phone as a panel. Panels are special interface mechanisms unique to Xperia; they allow phone users to interact with a specific web service or an application.

With this release, Facebook is now available on the iPhone, Blackberry and Windows Mobile (almost) platforms. No Facebook on Nokia’s Symbian or Google’s Android — not yet, anyway. 

I wonder how many people will actually end up buying the X1 device, which is about to go on sale. I returned the review phone earlier today so I don’t know how this app, which you can download for free, actually works. But I do know you can use it to check status updates, friends’ profiles, pics and notifications. Facebook on the iPhone remains one of the best mobile web apps — and even other versions of Facebook pale in front of its capabilities. (Read: my X-1 Review.)