I buy jelly rolls, layer cakes, charm packs and fat quarter bundles. I buy them because I can get one piece from an entire line of fabric that I wouldn't be able to get otherwise. It would be a daunting task to hunt down all 40 or more fabrics from a single line since the majority of quilt shops pick and choose from a line and don't carry the full line. I also buy lots and lots of yardage. I only buy single yards of things that are backgrounds or blenders where I'm likely to use several in a single quilt. Everything else I buy at least two yards of and most of the time I get at least 4.