Well, I opened a can of Bumble Bee tuna yesterday. In the tuna were two rther large pieces of either bone or shell, jagged pieces that would have been dangerous if swallowed.
I wrote the company, and I'll check food in the future before I eat it. I saved the pieces to send to them once I get an address.
I also found a piece of wood in a bag of spinach recently. And here I'd thought that it was only in Cracker Jack boxes that you got a surprise...