Audiogon is becoming the hub for scammers.

It’s the responsibility of the manufacturer.
Before you allow your blood pressure to rise from my comment please allow me to explain.

When you purchase a Ferrari, either new or vintage, the owner is entered in a registry so every owner is verifiable. The registry also contains maintenance and provenance data. Enter the VIN on the registry and every single detail of the car appears. If the last address doesn’t meet or match the current owner then you can be suspicious.

Pass Labs does this, McIntosh I’m not sure.

I’ve bought/sold hundreds of items through this site and others over the past 20 years.. I have never, ever registered any of it with a manufacturer including probably 10 Pass items. Many of these items change hands multiple times.  It is NOT the responsibility of a manufacturer to keep track of every item they have ever sold. It is ridiculous to think that they would or even could.

 PayPal is at present the best way to guarantee that neither the buyer nor the seller is cheated or scammed. A seller doesn’t get his money until the buyer has received his goods and is genuinely satisfied that he’s gotten what he was promised.

It doesn't work that way, never has. What you are describing is an escrow service, which PayPal is not. As soon as the money is in your PayPal account you have access to it even before you ship. You can use it to buy other things or transfer it out to your bank.

The buyer can come back and file a claim if not satisfied and PayPal can take the money back, but PayPal does not hold it until the buyer states they are satisfied. 

Yes well I bought a McIntosh preamp on Audiogon  used it worked for 4 months and is now Dead.

this is not what is meant by being scammed. If it worked for 4 months so you got what you paid for, it just unfortunately died. That happens a lot with used electronics. It should be able to be repaired.