While this isn't technically a format war story, it seems like it's the closest we'll get today.

According to The Digital Bits, some of their readers were reporting a slight mishap with the Harry Potter Collection Years 1-5: Blu-Ray set. Apparently, in some cases, the most recent disc in the set, Harry Potter and the Order of the Phoenix, was in fact the HD DVD version instead of the Blu-Ray disc like the previous four.