If .cc tells the whole truth and nothing but - then it should be easy to legally prove that they have their name used in commerce well preceding the registration? Not sure how the law works in the US but in Norway that's all it takes (more or less).
It is never that easy with Trademark law.
I have it on good authority from a trademark attorney that if Smart Projects are prepared to defend their trademark, then getting back the trademark from them will take upwards of 7 digits in the US.
It is a very real possibility that both companies will go bankrupt arguing over this trademark before anyone "wins".
Massimo et.al should just admit they got duped and move on, unless they have a deep pockets financial backer who is willing to fund the legal fight.
They should take up the Freeduino banner
http://www.freeduino.org/ declare it the new standard, and forget the name Arduino ever existed.
Let Smart Projects stand on their own with their "official standard".