Back in 2002 the FCC chose a standard for digital radio broadcasting called IBOC (In-Band On Channel), that many deride for being low-quality and destructive to adjacent analog stations, especially low-power stations.
Blogger Bill Middleton has an interesting analysis of the FCC’s poor choice in comparison to the system used by most of Europe and Canada, EU147 DAB. His informed outsider’s perspective–he’s living in Norway–is valuable since he’s actually heard and experienced the benefits of the EU147 system.