My parent's house is nightmarish in this regard. You simply can't get into one of the rooms, and it's difficult to walk across the hallway without bumping into anything. For a while, I had to squeeze past a chair with a huge unstable pile of newspapers right in the middle of the hallway just to get into my room. There's also a bookshelf in the hallway leading from the kitchen to the laundry room
Other areas are similarly crammed. Every available inch of surface area in the entire house is covered with objects, often with deep piles (like on my dad's desk). and much of it is unstable and ready to fall down at any time. All floor areas not being used for basic navigation are also filled with junk. Every closet (including about half of my own, while I was there!) is filled with my mom's old clothes. They also have a garage and 10x10 storage unit, which are filled to capacity. My mom even has a second 10x10 storage unit with my grandmother's stuff that she inherited a few years ago.
If I ever visit, it takes at least an hour just to clear enough room to put down an air mattress.
Ugh. I feel sick just thinking about it.
...and I have to admit, I've picked up some hoarding tendencies of my own. I have hoarded videogames, magazines, computer game boxes, comic books, text books, DVDs, computer parts, cables, household goods, and more. At its height, my DVD and comic book collection filled the walls of an entire walk-in closet. I had a second closet dedicated to videogames, in addition to several shelves.
Before moving, I got rid of the boxes and magazines, and a lot of the foreign language comics. Since moving to California, I've thrown out nearly all of the DVD and CD cases (keeping most of the disks) and put them into binders (which still fill up most of the top shelf in my (much smaller) closet), the unused household goods, old clothes not in wearable condition, the my classic videogame collection (besides some choice rare titles, but all actual gameplay is now through roms, since the systems are gone), and more. Before anyone asks, I gave the games/systems to some friends of mine.
Even so, my room is still pretty full, but I'm still trying to cut down.
I actually spent most of yesterday trying to manage all of the clutter. While I didn't throw away anything other than trash and receipts (I hate those things), I did move several piles of books to the storage shed, so that my textbook shelf no longer has books stacked on top of other books on the top shelf, or overflowing onto the floor.
It's also kind of annoying that in my, you can't dispose of more than about two full kitchen trashbags in a week, which is in a way pro-hoarding. Most of the stuff that I got rid of was during the annual "trash week", when the city drives huge moving vans though the city to pick up anything that people want to throw out.
Yeah... I have problems too.