We hear that Chris Shipley and the rest of the Demo conference team are coming down hard on companies who violate their exclusive contract. A tipster "has it on on good authority" that one presenting company has been "yanked off the stage" at tomorrow's fall Demo conference in San Diego, because it demo'd its wares at Michael Arrington and Jason Calacanis's competing TechCrunch40 conference last week. No surprise there: The whole point of these startup-demonstration conferences is to show something new, and an already-launched product won't make the cut. But Shipley's crew is being especially tough: We hear that the company isn't gettting its $18,000 entrance fee back either. So who is the culprit? And did they make the main stage, or did they lose out on Demo just for debuting in TechCrunch40's also-ran DemoPit? If you know anything more, fill us in.