I'm careful now because my financial situation is not great, but I do have a certain tendency to accumulate useless amounts of versions of a few things. Generally books or music I like, but it's not necessary my top favourites. I don't necessarily know why I compulsively collect some and not others.
Books: I have to get every version of the original, or of modern English translations, of Beowulf and of Gawain and the Green Knight that I came across. How could I let one behind?
Music: the worse culprits are Elgar's Sea Pictures and Mahler's fourth symphony. At least, with classical, I collect different versions. The same can't be said with metal. I have many variations of the exact same albums of Opeth, Orphaned Land and Ne Obliviscaris, some unopened, and I still feel compelled to buy any new edition. This is fully ridiculous. A lot of them are vinyls and I did not get my turntable out of storage for years...