I just read a very provocative blog about whether data quality is an IT issue and the author has a good point. See http://www.dataqualitypro.com/data-quality-forum/post/667593
Of course data quality is a business issue but that does not mean that IT is not intimately involved. Often the business rules specified by the business are not impemented correctly and sometimes the data validation routines are incorrect. There are numerous other examples, but in the end the business must make sure that these errors are corrected by IT. Often these errors do not show up during testing but later when the application is being used.
Often the phrase that data quality is a business issue is interpreted as IT not acknowledging their role. Nothing could be further from the truth and the business must work with IT to correct the data quality issue. Often the responsibility is shared and must be resolved by the groups working together to resolve some very complex data definitions and business rules. Effective data governance is an effective team effort with everybody working together to deal with issues rather than placing blame or pointing fingers.