They said they would give the Magicka keys to 3 random participants. If you're friend didn't get a key then it's just bad luck I guess. If those 3 guys disappeared with the keys after signing out well there isn't much anyone can do about it.
I don't quite see how this could be a scam, they're not asking for money / credit card # or whatever, instead they're giving stuff away.
Not all tourneys are designed to please everyone. And yes this is maybe a bit poorly organized but I'm sure sure ActionRadius will learn from their mistakes. Besides, if they're trying to attract more people into Magicka then who can hate them

?
"Win Magicka game just for registering for this tournament
Don't have Magicka but want to play it? 3 early registrants of this tournament get a free copy of Magicka. Already have Magicka? then why not tell your friend about this offer to get them a free game and play in this tournament.
Login on ActionRadius using Facebook login button on top. Click your name / nick on top. Edit your profile and ensure that your correct steam username is setup there. This steam username is where you will be sent your free Magicka copy
Join this tournament
Post a comment on "Discussions" tab of this tournament that you registered for tournament and want free game.
Once you do that, then just wait till we check your records. If you have joined the tournament, your steam id is setup, your steam profile doesn't already own Magicka, and your comment on Discussions tab confirm that you were one of the 3 early registrants then you will be sent free Magicka steam code."
They did say these free copies will go to 3 early registrants, you can argue its not the same as saying "3 first registrants" but then how are they chosen? Is there a lottery? If you look at discussion tab on Action Radius site you will see all of them (winners and the person responsible for sending those keys) are the same nationality.
Obviously its a scam as someone wants to grab those nice free copies of Magicka (which were sponsored by Paradox) and I wouldnt be suprised if winners of the tournament turn out to be some unknown turkish/arab guys who cant play the game at all.
Im from Poland, we do these things all the time - dont be naive, this whole tournament is a farce.