I had THREE Schwalbe Marathon Plus 700x28c's, apparently from at least two different production runs (logo changed) come apart where the rubber casing over the bead meets the rim. This happened on two different Velocity Dyad rims, and never over a couple of hundred miles on any of the tires. BAM! Two blow-outs and one deformation caught before the blowout.
Downright dangerous, and doubly so on a tandem. My LBS took them back, gave me credit, and was going to show them to their Schwalbe distributor.