Mixed feelings but if someone gives you a plug and tells you to do "this" with it you should do "this". MAC would sometimes come up and say "Fish This" - it got fished, sometimes he'd say use these for the site as you see fit, they went to the site.
As far as flipping plugs up on fleabay? I have some real nice stuff that I've gotten over time but unless I was in financial emergency I could not make myself put it up. 90% will get fished (though as of late I tend to make sure I keep one example from each guy
)