Would this warrant bad feedback?

Not once or twice but thrice over the last 6 months, a member has re-niged on trades or buys. And he didn't even let me know about it.

If someone says "Ok, I'll take it. You will have payment tonight" they should at least let you know if they don't want it right?

Would leaving negative feedback be too much?

FYI

This member has done a few deals. As far As i know, he hasn't done this to anyone else.

well he would be labeled a timewaster. Not a scammer. But bad feedback should be given,

Well no product or money was lost. I agree it wastes time and could get in the way of potential sales/deals while you wait but Negative feedback is a bit much. I would probably go for Neutral (it still stands out) and give explanation about poor communication, etc.

I'm used to timewasters but This guy irks me for some reason.

I've had bad transactions with some notorius timewasters before and never said anything.