I agree with Ehab. Spotters really need to be skilled in the art of model jets to be effective as a spotter. Personally, I only feel comfortable with a few friends as spotters, since you know what to expect. Alternately, the worst spotter is someone you don't know and he thinks you're inviting him out for a chat while you're concentrating on flying your jet.

I did a local full size airshow this last year and brought 2 guys with me as spotters due to the increased level of potential liability... It was sanctioned, but it never hurts to be safe. One was there just to look for unannounced full size aircraft (a non jet guy), and the other owns and flies the same model so he was pretty well just watching my jet for anything unusual.

That being said, everyone's got their own criteria for a spotter, so a few event supplied individuals might be a really nice touch for some.

Kelly