Usually I'll only buy fabrics I need for a project. Once in a while I'll buy something I have no idea what I'll use it for, but only if I really, really, really, REALLY love it.
Was tooling around eBay to see what they had for Moda marbles (for my stained glass project I've been obsessively planning out) and ended up buying a bunch of purple fat quarters for no particular reason. Though right now I'm staring at my autographed Kittie poster sitting on top of the wire shelf at the foot of my bed (the shelf and poster was put there after my TV fried out a few days ago) and for some odd reason "black and purple Cathedral quilt" comes to mind---my only theory to that is the drummer's favorite color is purple, wears black (like the rest of the band), and has Jesus and Mary tattooed on her feet, but either way the idea sounds FANTASTIC.
And several days ago I bought some hot pink and bright orange Moda marble fat quarters thinking that maybe they'll match with my project. "Maybe they'll match with my project"? I've been painstakingly trying to match colors like a purist madwoman and then I just pick out and buy two fabrics on a whim without even looking to see if they match and without knowing how much I need yet. What the hey?
Then it just hit me. I think I'm...stash building.