Are you getting ridiculous offers from new members

Respond with a counter offer higher than your asking price

Ha, I have done that before, it was fun. Got a nasty response, don't care.

I'm new... what is considered a lowball offer? 5% off asking, 15% off?
If anything below asking is lowball, then why have the feature at all?

I've watched two offers expire with no response, then watched the item expire only to be reposted with new ending date.

At least now I understand why I didn't see a rejection email. 
I didn't intend any insults. 

PS -  it was a pair of used speaker cables

@dumes    
Don't get discouraged by one seller. Some are likely leery of zero feedback buyers. To me, it is foolish to pass up any buyer that has interest in gear I have for sale. If I have it listed with an offer, then I am leaving some room to my bottom line price. If the offer is reasonably close to my bottom line, I try negotiating. If the buyer doesn't move from their offer, I move on. I have sold multiple times to low or zero feedback members without issue. I always make sure I establish some communication with them to get a feel for them before committing one way or the other. As to the question of what is a lowball offer, I suspect it varies from person to person. Some are obviously sensitive to it. I have come across people like the OP is referring to. I recently had a 15 year old piece for sale that I listed for 1/4 of it's MSRP, yet had seen the piece sell consistently at or above my asking price. I received an offer at 40 percent of my asking price. That is low ball IMO and I just immediately hit the decline button with no comments. I didn't get upset, I just declined. I also agree with the OP that more of that kind of offer is occurring here as of late. 

agree with Mr. Golf. Lowball is in the eye of the beholder. Some list items way over what the market is just to see it they can grab a sucker. I offer what it is worth to me. If the seller gets angry about my offer that is their problem. If I get what I consider a lowball offer I politely decline. Some of those turned into sales close to my asking price. Telling a low baller to go shove it accomplishes nothing.