Here's my 0.02
  Asking for technical advice from the list, getting it, and turning
  around and selling a fixed item, to... eBay, is Most Rude.
  Letting the people on the list save time on searches by making
  small inobtrusive FA announcements:  Offers a slight benefit.
  Offering things to the list first, waiting for responses and then
  resorting to eBay is Most Generous.
John A.
looks like a balancing act.  see: "Ethics"