The FDA issued a summary of 2010 Medical Device warning letters data by section of the regulation involved. The full report is at the link provided. 8% (7 of 89) of Warning Letters had citations related to 820.70(i) which validation of production and quality system software. 81% (72 of 89) of warning letters included citations for Design Control with the largest subsections cited being (i) Design Changes and (g) Design Validation. The report does not break out Software Design Control as a separate category.