Here's a great article about owning too much stuff by Paul Graham:
I first realized the worthlessness of stuff when I lived in Italy for a year. All I took with me was one large backpack of stuff. The rest of my stuff I left in my landlady’s attic back in the US. And you know what? All I missed were some of the books. By the end of the year I couldn’t even remember what else I had stored in that attic.
And yet when I got back I didn’t discard so much as a box of it. Throw away a perfectly good rotary telephone? I might need that one day. …
[Stuff can be] worse than worthless, because once you’ve accumulated a certain amount of stuff, it starts to own you rather than the other way around. I know of one couple who couldn’t retire to the town they preferred because they couldn’t afford a place there big enough for all their stuff. Their house isn’t theirs; it’s their stuff’s.
This article hits particularly close to home to me right now. I still have several boxes to unpack from my move to Arlington and am not sure what's in several of the boxes. I also still have a bunch of boxes full of mystery items in my parent's basement.
One of my roommates just moved in and has a ton of boxes from floor to ceiling in our living room. The bad news is that it's clutter. The good news is that it makes me feel better about the smaller number of boxes I have. (Hmm... is that a reverse form of this going on?)
Similar to Paul Graham, I have traveled the world with only a carry-on backpack and have rarely missed any of the stuff I left at home.
I've now stopped accumulating stuff. Except books—but books are different. Books are more like a fluid than individual objects. It's not especially inconvenient to own several thousand books, whereas if you owned several thousand random possessions you'd be a local celebrity. But except for books, I now actively avoid stuff. If I want to spend money on some kind of treat, I'll take services over goods any day.
Also like Graham, I have a weakness for books and a penchant for spending money on experiences (especially travel) rather than things. (Something Harvard's Daniel Gilbert says may be the best way to use money to increase happiness.)