As the founder of Free World Dialup many moons ago, Jeff Pulver knows open. As the founder, owner, and impresario of the VON (Voice on the Net) Conference, Jeff knows promotion.
Now he's putting the two together with an offer of a promotional opportunity at the Fall 2007 VON to whoever first puts together an open iPhone which can accept SIM cards from networks other than the network it's originally locked to (at&t in the US) and which can support a SIP client to allow VoIP calling at WiFi hotspots.
Fred Wilson started this by offering a promotional opportunity on his blog for anyone who could offer an iPhone which freely accepts "foreign" SIMS. I am offering a promotional opportunity on Fractals of Change for an iPhone which allows VoIP at any WiFi hotspot a computer can log on to.
iPhones opened in these ways are, ironically, not likely to need very much promotion to be a big hit.