That's one that didn't immediately come to mind for me. I gotta admit, I almost certainly would pay for that (although it's almost completely hypothetical since paying for it goes completely against the entire philosophy of the service, and if it had always been a pay service, it wouldn't be as extensive).
If you did have to pay (I realize this is hypothetical), what if they charged per article you read and you got a free read when you contributed? Or part of a free article when you edited. Would that help to keep it extensive?
