I do everything in my power to never list stuff for anyone, at anytime.
First, after the fees are taken out, the consignee never seems to be happy with the deal. For instance, a good friend was having a garage sale. She had 3 packs of Polaroid film marked 50 cents each. I told her that they were worth far more than that, and she suggested that we split the deal after ebay fees were taken out. Her cut was $48, and while she was happy, I could tell that she thought the selling price was too low, and that the ebay fees were too high. (We got tip top money for the film at the time.) Even though someone could have bought all three packs for $1.50 at the garage sale, and she should have been thankful for my help....there was just a tiny bit of rift over the deal. I'll keep my mouth shut the next time.
Second, I pay taxes on my ebay earnings, and selling on consignment is a pain at the end of the year.
Third, I've worked hard to have an almost perfect 5 star rating. I am proud of that, and I don't want it messed up in any way with someone else's junk.
Fourth, what are you going to do when you sell those CC dollars to someone, and they report you as "item not as described", and send you back a bicentennial Ike, and keep the CC?
Lastly, there is just too much for me to list that I already own. No need to take on someone else's junk so they can get mad at me at the end of the day.