I don't take any of it personal. We are talking about buying and selling things to people who are most likely NOT like me or you. CL has opened up the market place for every walk of life to deal with regarding buying and selling.
Times are changing and if you can't deal with people who do this, then don't do it. People are called CL flakes for a reason!
I usually ask if they have movement on a price when buying something or I ask if they will take "this much" for the item. I have bought many things without seeing it first and making an offer that was accepted. I am picking up a door for our house today and the deal was made over emails. If I show up and the item is what they said it was, then I buy it, and if I show up and it's nothing like what they said, then I negotiate a lower price, or tell them sorry I don't want it.
Life is too short to be concerned with the changing market place and how people deal with each other.