bad form? Hell no. I walk in most places and ask to speak with the owner, then proceed to ask if they have any broken or empty cabinets, or games that just don't make them any money they want to get rid of.
Lately, the answer is, "I just hauled off four to the dump."
The last four in question were Soul Calibur, a Neo Geo 1-slot with Metal Slug, a Galaga, and something else.
What makes me mad is my mother knows this person and I told her to pass along the word to them (about 6 years ago) that I was looking for cabinets.