With all the BS from buyers, I dont see these seller tactics being a big issue, as long as its within ebay policy.
If you were in front of me and we haggled price from 100 to 30 in your favor and agreed; then I changed my mind and wouldnt take your money for it you'd be miffed but in reality no harm was done.
Not saying i ever do this stuff but just pointing out that in reality its not a done deal. We as sellers are supposed to just put up with non-paying bidders like its their right.