I do think Prosfilaes has a point. The primary interaction that any player will have with the game world will be through the rules, whether those rules are filtered through the GM or not.
I'll probably want to come back to this at a latter point, but I disagree. The game world generally isn't even discoverable from the rules. It's not in there. And, with the exception of a few GMless systems, if all you are interfacing with are rules and not a GM then you don't even have a game.
Player 1 plays in a system where the rules are very open to all players and he knows the books reasonably well. He comes to a pit. He knows, from the rules that this fall will not do enough damage to kill his character. His decisions about how to cross this pit will incorporate that information.
Ok. That's unavoidable.
Player 2 plays in a system where the rules are kept hidden behind the DM wall. He comes to a pit. The first time this happens, his decisions will be based on guesswork. But, after he falls in that pit the first time, the second pit trap he comes to will no longer involve guesswork. He knows the rules now and he's in the exact same position as Player 1.
No. Don't get me wrong, I'm not arguing for a rules wall here, but you are just wrong.
Consider for example what you know after falling in the pit once under my rules. You know, for example, that after falling 20' that you took 12 damage. So, you might say, "The rule is that if I fall 20' I take 12 damage." But, you'd be wrong. You have only one data point. You as of yet have no idea what the range of possibilities are. Maybe I threw 2d6 and you got really unlucky. Maybe I threw 2d100 and you get really lucky. You have no way of knowing what the rule is, nor do you now how it scaled. For example, you might suppose that the rule is, "You take 6 damage for every 10' you fall." But if I'm using the common cummulative damage rule, the 30' fall will do on average twice the damage of the 20' fall. That's not a feature that would be obvious from the rules. Under my rules the actual damage range for that 20' fall was 0-40, and there are emergent features that might not be immediately apparant.
What is gained by hiding the rules behind the GM wall?
Let's try not to drift too much from the topic. We aren't actually discussing the utility of rules walls generally, which I wouldn't support. What we are discussing is attracting new players to the game, and in that situation an actual 'rule wall' isn't useful but it is I think quite useful to approach playing the game from something other than a rules first perspective.
After a very short period of time, the rules will be known to everyone at the table and both groups will base their decisions on that knowledge.
It probably won't be nearly so short of a time, but yes, it's inevitable and even useful that the players will eventually acquire some knowledge of the rules.