Jeffh has pretty much got what I meant. "Blue sky" - without restriction or guidance, ex nihilo. As in "out of the clear blue sky" and "the sky is the limit".
The best example I have comes from the Star Wars Saga Edition game I play in. One of the players is not actually specifically a Star Wars fan. She saw the original movies when she was a kid, but that's about it. She's never re-watched them. Didn't watch the prequels. Never read an EU-novel. So, she knows there are Jedi with laser swords, and non-Jedi, wookiees, space ships, and an Empire, but not a whole lot more than that. The GM, however, was overly committed to not structuring player experience...
Player: So, what kind of character can I make?
GM: Well, you can be anything you like.
Player: No, you don't understand - I don't really know the setting. I need a little help.
GM: Don't worry. You can be anything you like, really.
Player (frustrated): Fine. I want to be a Centauri Dancing Girl, who, as a child, was a slave to a mad Fagin-bot who managed a Dickensian group of child-pickpockets...
GM: Well, there aren't any Centauri.
Player (now bordering angry): But you said I could be anything! But clearly I can't be *anything*! So, what can I be?!?
In the end, we adapted her basic concept nearly directly (she's a twi'lek dancing girl, and the droid is now F4-G1N), but both the player and GM were extremely frustrated and confused, to the point of the game almost never happening at all.
The fact of the matter is that games and GMs generally have some implicit expectations about characters. If the game and/or GM are not up-front about it, it's a pain in the rear. The Marvel game itself is not terribly up front about its expectations - it leans very much on knowledge of the Marvel Universe, and understanding the rules in full *before* creating a character. It really really wanted for a more structured character generation system in the core rules.
