The thing is...people like me are DMs...yet we might play in someone else's campaign. If I DM and play in an Eberron campaign is it that big of a problem that I know some of the secret knowledge from the ECG? In fact, I get more enjoyment out of playing if I know some of the backstory...even if my character doesn't.
And if it isn't that big of a problem, and in fact, increases the fun aspect of playing for me as a DM from another game to know secret knowledge, it's just a small step for increasing the enjoyment of the players themselves.