That's pretty much my opinion.

A couple factoids: Apple's 30% number is pretty much the same as Facebook's number for their virtual currency, and Facebook also requires that folks like Zynga must use Facebook currency. (Last I checked, anyway, but I don't follow that stuff very closely.) So, at the very least, there's some precedent for this sort of thing.

I'm no lawyer, but I would expect one or more major Apple app vendors (Amazon? Rhapsody?) to do literally nothing. No app updates. No in-app payments with Apple infrastructure. In effect, one or more of these vendors will play chicken with Apple. If Apple takes their app down, they sue. If Apple leaves their app up, they move on with life. If Apple rejects an update to the app that leaves the status quo alone, then they sue. Lather, rinse, repeat. Similarly, you could expect some vendors to violate Apple's terms and have higher prices for in-app purchases than external purchases, even going so far as to say "it's cheaper if you do it from our web site." This just dares Apple to file suit. Put that in front of a jury, and Apple won't do so well.

That ultimately leads to a negotiation. firms like Amazon are big enough, and enough money would potentially be moving through this system, that they can negotiate directly with Apple and have their own private agreement. Whatever happens in the end, Amazon isn't paying 30% to Apple, not when they've been fighting tooth and nail over sales taxes that are much lower.

If Apple somehow manages to maintain the 30% number and require the in-app payments, you can also imagine a variety of companies being incentivized to subsidize you into an Android device because they make more money on the back end. How many vendors might pitch in for such a subsidy? Would Microsoft try to get in on this game to pitch WP7? Sure, why not?