A recent tweet has us positively giddy at the thought of being able to tether Windows Phone 7 devices over USB without additional contract costs. Granted this is an unsubstantiated rumor, but it isn’t entirely farfetched either.

The tweet states:

Official word--Windows Phone 7 will support USB tethering, carriers can NOT charge extra, above the data plan.

Just to throw some fuel on the fire, perhaps this is a contributing factor to the AT&T data plan changes from June. Given the fact that AT&T is described as “the premiere launch partner” and is rumored to be on the receiving end of six different Windows Phone 7 devices to the tune of 8 million units; I'd like to believe there is some truth in the rumor.

What do you think? Ridiculous or plausible?

Update: The source of the original tweet, Richard Dudley of ComponentOne, tells me that his source is one of the Windows Phone 7 FireStarter events. Have any of our readers attended one of the FireStarters?

Update 2: Apparently, there was a misunderstanding of some kind. Mr. Dudley tweeted this morning that tethering "is not official, may not happen." Chances are that this will be something that carriers can optionally enable at minimum, though I like the way that Microsoft has been throwing their weight around.