1. Apple juice. I have an antique oak kitchen table with a small oak lazy susan on it. It was finished with poly ~25 years ago; the finish has held up very well. Until my daughter spilled a glass of apple juice under the lazy susan. It sat there undetected for who-knows-how long. When detected, the poly was totally gone.
2. Room perfume. My dad and I built a pine box to hold a set of geological maps, ~1976. It too was finished with poly. It's been knicked and bumped a bit, but the finish was in pretty good shape. I temporarily stored it against a wall, underneath one of those plug in gizmos to make the room smell "better". (Well, better than cat odors, I guess). The oil leaked onto the top of the box and down the front. The poly was cleanly stripped down to the wood.
Just keepin' the group informed.