Mine is books, GOD DAMNIT but its books, I think I've got four square feet of free space in my room a the moment, and its not a big room to begin with, for the stacks upon stacks of books, you know what else, a big part of the addiction revolves around non-fiction so when the author recommends, even just mentions, other books then I'm onto getting copies of them too, novels, well, the author may mention books which the characters are reading, there's a new lead, the author may have other books out, there's a lead too.
Plus there's a shit load of vacarious living done through books, thinking of travelling some place? Taking up a new hobby? Developing a new facet of your personality? Networking or meeting people? Any experience you can think of, there's a book for that, and of course I wind up buying it, may never do or see or whatever the subject may be and discover the books later when I'm not even interested in that shit anymore but hey I'm sure someone is shopping the charity shops I dump them all on and maybe they'll have more luck than me with that.
Then there's so many books you cant find the one you planned to read, perhaps maybe get a second one to add to the chaos, damnit.
On the plus side, the only plus side, I'm pretty sure this is hurting no one, unlike a lot of vices, and it doesnt actually stress me that much, most of the time, which is a good thing too.
Although it breaks my heart that I wont probably have time enough in a single life to read all the books (yes, all the books, all the books IN THA WORLD, and KNOW all tha things IN THA WORLD, welcome to my crazy).