I have a friend of a friend who is a hoarder. Recently, she got a flat tire and was unable to get the spare tire out because her car was so packed with junk. Her house is barely livable. I feel sorry for her.
There are specially trained counselors out now who try to help these people. They get rid of one thing at a time, because it is supposed to be too traumatic and stressful to clear out everything at once. Many times, they have a relapse, and within months the house is back where it started.
From what I understand, hoarders have had some kind of trauma in their lives that cause them to behave that way.
There is a program and books about hoarding out now. Interesting subject.