Not sure why this wasn't a consumer recall issue, except for the fact that the defective harmonic balancers fell under a certain serial number range.
I'm not sure what constitutes a recall by definition, but I suppose if a part had been deemed defective in ALL particular vehicles it was installed in, then the recall option would be in effect.
I can only guess that the techs here are better equipped to gauge the failure rate of that part since they do the replacements.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car