Is a offer of -20 percent on an OBO ad insulting?

Tweekerman, brings up good point. If a piece is put up for sale with "o b o" then a negotiable sale is implied.

In any given instance - yes or no.

Assuming the price is listed out fairly, an offer of 80% is insulting.

Lets take a Nordost Quattro Fil cable of 1 meter - they usually sell for between $750 and $800 on Audiogon. Assume a listing price of $750, and an offer of $600 - that is ridiculous, and not worth a reply.

Of course, the seller takes a risk of never selling the product too!

OBO means offers are being solicited. No, but I will take X is far easier to type and much more appropriate than the flaming you received. I vote for "putz" and agree that you are better off w/o him (esp. for a high availability item).