I beleive the keys will be offered in a apropiate fashion linking back to the ammount of user createed content that will be published at the start of the beats. I am not exactly sure how much of that will be possible.
From what i read there will be legal wavers for testers to electronically signed or faxed? (hasent been decided). By which any publication of the game will result in you getting sued. (Not something you want happening).
But i am sure reverie will supply an adaquate amount during beta to meet your needs
And that the user data will proably be sent to a reverie mod to beto or aprove before being published.