What's up with the ridiculous offers?!?

Meh not that big a deal, I either decline or make a reasonable counter-offer. Seriously nothing to lost sleep over.

"Is this a new feature in Agon? Listing AUTOMATICALLY negotiates by itself once listed?" 

No, but listing something for sale commences the sales process thus is the start of the negotiations process because the seller is posting at a price point. 

I do do not and have never advocated negotiating against ones self

IMHO, it began in earnest when cell providers started 'giving away' cells with contracts.  People noted the retail price of the item, and began to think that this sort of pricing might apply to any electronic item.  This line of reasoning was augmented by the pricing applied to flat screen TV's.  What used to be 'pricey' would be marked down so quickly that it would appear that anything a year or two old in terms of it's appearance on the market was now available for a song....and not even one sung well. *L*  And i've not even gotten to the 'haggle factor', because they don't know if you're serious even if you've posted that it's not up to negotiation.  If priced fairly, those that know will respond appropriately.  Those that don't, or just want to jerk your chain to see if you'll bite can be dealt with however you feel is or isn't worth your time.  We're in the 'buyer beware' era.  Nobody wants to get hosed, but nobody wants to give things away, either.  This sort of 'combat zone' exists on our freeways in a related fashion.  Most will 'play nice', but there's the few that seem almost psychopathic in their approach to driving.
I'd prescribe a grain of salt, but modern society seems to have inflated that to the size of a salt lick BLOCK.  Just roll with it, and channel your better self.  You'll sleep better... 

The annoying part for me is getting messages stating something like "if you can lower the price to x, I will take the item".  When I do respond with "yes", they never make the offer. Now, I just decline ridiculous offers and tell the others to make a formal offer using the Agon process and I will consider the offer.

Greg, there you go.  You do what you deem appropo.  Just because 'we' can act uncouth and annoying, doesn't mean you need to stoop.  Your game, your game plan....run it. ;)