Someone on this forum mentioned that Weber is being pretty strict on the SmokeFire in regards to the warranty. Meaning, you have to provide proof of purchase that YOU bought the unit. That's one of the reasons I'd be leery of buying a used unit, unless it was a really good price. I think having a warranty on this model is really needed with the potential issues.
Much more difficult than the warranty for a gas or charcoal grill, where you just plug in a serial #.