The radial has been commonly fitted on larger cars capable of very high velocities (or "sport-type vehicles" as the AFX News Limited article confusingly states). The Michelin in question has been used as an O.E. fitment on cars like the Audi A8 and Jaguar XJ8 in Europe over the past three years.
Apparently, a sidewall blister can lead to a tire going flat rapidly [read: blowout]. No accidents due to the defect have been reported, but the (lucky) owners of these high speed projectiles are advised to turn them over for suitable replacements at once.
[Source: AFX News Limited via Forbes.com]