I brought two bags to Amsterdam at the end of September last year. I bought a bike and a few jackets. Then I got a job (30 month contract). So I returned in January, emptied my storage unit, sold most of my stuff (except the BMW!), and put the rest into "my room" at my Dad's house. By volume (excluding the car), I got rid of 75% of my stuff. I kept photo albums but got rid of lots of kitchen gear, computer, DVDs, books and clothes. The remaining stuff is too personal and timeless to sell or toss, but even now I don't miss much of it (I brought three bags over, filled mostly with clothes).
I think that others' answers to this question reveal more about the way they see possessions, "home" and permanence.
I guess a similar poll would ask people what they do with books once finished. I always rush to get rid of books I've read -- partially because I want more empty space, partially because I like it when people use things up. Other people love to hold onto them. Some people reread books later, others lend them out, but many -- I suspect -- just like to see them on the shelf.
Bottom Line: Possessions can be comforting, but they can also stifle mobility.