Autolycus wonders what a "blockage" is: they're talking about intestinal blockages, where the intestine is obstructed and the digesting food is prevented (blocked) from moving along through the plumbing normally. The term can apply to a partial or complete cork-up. The parts of the digestive system that lead up to the blockage continue to operate normally until the intestine fills with food, fluid, gas and secretions. The intestine enlarges, the lining swells and becomes inflamed. Untreated, it can rupture and all the stuff inside leaks into the abdominal cavity, where it causes peritonitis and infection. If the obstruction crimps up the intestinal wall and cuts off blood flow, gangrene can set in. Eventually a person can die from the results of a blockage. (Info came from this site)

How can all this happen from a teensy little Polly Pocket magnet, you may ask? Apparently the problem occurs when a child has swallowed more than one magnet, and they attract one another and clump up. According to this article from the U.S. Consumer Product Safety Commission, three children were reported to have had required surgery because of having swallowed multiple magnets which caused perforations in their intestines.

I wonder if it's possible for the magnets to pull toward one another through a pinch in the intestinal wall, as larger magnets would do through a folded piece of paper?