People are people, it's naive to think that good guy's are on Audiogon and all the crooks migrate to eBay. If you exercise some diligence you can trade on eBay without significant risk. The feedback system works just as well on eBay as it does on AG. Anyone who has consistent positive feedback will work hard to protect it, and you should be able to trade with them without worry. Someone who has not established much of a reputation through the feedback system may not have the same desire to preserve their feedback rating and might represent more of a risk.
Remember that eBay is a much larger community than AG, so you're exposed to a much larger mix of people.
If the feedback system isn't enough, you can often guage what a person is about by the way they construct their ad. Is the person clearly knowledgable about the equipment they own, have they provided suitable images, are they responsive to emails, will they provide a telephone number etc.
It's common sense and there's no need to get burned if you use it.
I've been trading on eBay for several years and for a little longer on Agon. I probably have over 300 transactions on eBay and only 20 or so through Agon, yet my one bad online experience was through Agon.
There are exceptions to the rule in any situation.
Rooze