I think I started my stash because one of the chain fabric stores was closing and had a huge sale. I couldn't pass up the 75%-90% off pricing on the fabrics, so I grabbed a 1 or 2 yard of one or two fabrics that I liked even though I was not sure what I was going to do with them. Then I decided I needed coordinating fabrics to go with them in case I decided to use them in a quilt.
It just took off from there. Basically, if I see a fabric I like I try to buy at least a fat quarter of it.