Just to show that interference isn't restricted to HD, I post this link to a story about the group that knocked down an AM radio tower in Everett Washington. They claim the reason they did it was because of the "harmful interference" caused by AM radio waves. Methinks their problem is deeper than anything cause by interference. But that's just me. Just FYI, the station affected doesn't broadcast in HD.
http://www.cnn.com/2009/CRIME/09/04/washington.towers.terrorism/index.html
http://www.cnn.com/2009/CRIME/09/04/washington.towers.terrorism/index.html