I think you're misinterpreting Joe Kraus. I've seen him do his "Startup Addict" presentation twice now, once at Startup School and once at a YC dinner, and in neither instance did I come away with the impression that he meant you have to start making money immediately.
The meaning I took from this "business model in beta" statement was, "you have to be willing to admit you don't understand how you're going to make money; be willing to evolve the business model based on what you learn after launch". Which seems entirely consonant with what pg has said.
Quite possibly I am. I thought he was saying this after not releasing his premium account types for JotSpot initially and getting different feedback than he would from people actually willing to pay.
Anyway, I think the "beta" aspect of that statement is "try it and see, and change it if it's wrong". If your business model is "everything is free and I hate ads", then you'll soon find out that it's wrong. ;-)
It also ties into Kraus' favorite saying: You make what you measure.
The meaning I took from this "business model in beta" statement was, "you have to be willing to admit you don't understand how you're going to make money; be willing to evolve the business model based on what you learn after launch". Which seems entirely consonant with what pg has said.