The feeling of wrongness one feels when accepting something from a vendor for free/ payment optional where the person would otherwise be perfectly fine taking it from a third party for nothing.
"Hey man I looked up that album you told me about on the bay and couldn't find it."
"Why not get it from their site? It won't cost you anything."
"It's, I dunno, the principal of the thing, y'know, it's..."
"Pirate's guilt?"
"Aye."