I wish facebook had a system where the price goes up for a particular buyer every time they message me. I listed my collection of Magic The Gathering cards and this has been a conversation, I've had at least 50 times:

Buyer: Is the item available?
Me: Yes, when would you like to stop by and look at it?
Buyer: Can you give me a better description and take more pictures?
Me: Sure, here you go.
Buyer: Do you have _______?
Me: I'm not sure, I haven't played for over fifteen years, but you are welcome to come and look though everything before purchasing
Buyer: Is this the lowest you'd take?
Me: I don't negotiate with myself, but feel free to make an offer.

Then it's one (or a combination) of the following...

Buyer: I thought you were closer.
Buyer: Will you ship.
Buyer: *nothing*

It's not bad once, but when you have this same conversation 20 times, without a single person actually following threw it's annoying. I swear everyone just wants the ability to buy something. They don't actually want to buy it, they just want the ability to buy it if at a point in the future they decide they really want the item. These are the same people who get mad when the item actually sells. "...but, I told you I was interested." That's great, but the other buyer wasn't in a 2-week negotiation period. They just showed up and paid me.