Just so y'all know, Apple's already "fixed" (or "broken", depending on your POV) this way of enabling tethering for 3.1, <a href="http://www.macrumors.com/2009/07/15/iphone-3-1-beta-2-disables-unauthorized-atandt-tethering/" rel="nofollow">http://www.macrumors.com/2009/07/15/iphone-3-1-beta-2-disabl...</a>