that even if you do not use pesticides on your property many people do and insects can fly quite a distance - especially where light and pheromones are involved. Also, be sure you know what the insect is before feeding it to a herp. Rule of thumb: combinations of black/red/orange are usually warning for toxicity or other defense.
I just recently purchased a Bug Napper as well, and I'm in love with it. It's really convienant to just collect the insects in the morning, and feed them off whenever. And hey- if you have too many, you can just let them go and not worry about it. Plus it's a great variety in your chameleon's diet. I say go for it.
I live in a pretty rural area on a few acres. I don't have a whole lot of neighbors, and the ones closest to me aren't exactly the pesticide type. In fact, the closest house to us was finished less than a year ago, and they don't even have a yard yet. The next closest neighbor just lets everything grow wild. We don't use pesticides either. I think I can safely assume that we are running pretty pesticide free out here.
I am guessing that if the pesticide dose was high enough, it would at least make your cham sick. At low levels, it might give it a headache, make it feel crappy.. but as long as those low levels weren't continually fed, the pesticide would probably flush from the system over the course of time. Luckily, we are well beyond the era of DDT and other really nasty pesticides. While I wouldn't be so confident to name pesticides as safe, they are safer than they used to be. All of this is assumption based on no fact, and I would love to hear what others think of pesticide poisoning...?