Air Duct Cleaning: Scam or Not?

Should You Have the Air Ducts in Your Home Cleaned?
Adams video picks-

http://www.youtube.com/watch?v=Omygm7z9fZU

http://www.youtube.com/watch?v=rNu6u8KiA-o

http://www.youtube.com/watch?v=yLV6tdjXzUs&feature=related

First and for most I want to suggest that if or when you hire a...