I've been collecting yarn for years and years and years. I have a hard time throwing away a color and usually, in my line of work (amigurumi) I will use just a little of this and a little of that. I'm really choosy about what color I want to use, so if I need a specific color I tend to buy a new ball of yarn instead of just using something close that I might already have. I've also been sent yarn from companies to try out, and I never want to get rid of free yarn! This has led to a giant stash!