Hoarding: a supply or fund stored up and often hidden away.
Last night I spent three hours helping my friend clean her diabetic mother's house. We worked on the kitchen the entire time, filled 9 or so 55 gallon bags with trash and still have hours of work left to do- just in the kitchen! Now, I respect my friend and her mother, so won't get into to much detail, but I thought I'd cry if I found one more can of chicken brother or evaporated milk! People stock up on things, forgetting they already stocked up on them twenty times before.
My parents are the same way, but their problem is letting go. They will keep things for decades just because they can't bear to part with them. I haven't figured out if it is a money thing- like they feel that if they don't keep it that they wasted money or if they really do thing they need twenty of everything.
I was starting to become a packrat clutter bunny myself and have seen the error of my ways. I now make a weekly donation of items to the salvation army and spend hours selling things on ebay... yet my house is still cluttered. At least I'm trying! I refuse to become a hoarder! And according to a doctor on Oprah a few years back- if you haven't needed to get something out of a box for a year, you don't need it.