This idea, reported by macrumors.com to have been reported by CNet, is long overdue:

A CNet blog claims that Apple is working with labels to provide more incentive for customers to purchase full albums -- or at least not penalize them for buying singles ahead of time.

One thing I've learned over my many long years (ha) is that no matter how unique a thing I think I've done, other people are doing it. I assume my album buying habits are no different. Usually I buy a single or two off of iTunes from a potentially interesting album to try it out. If I like it, and it's not new, I grab a used CD off of Amazon. Obviously, crediting those singles doubles the record company's pleasure in this case... not only do they have a more competitive alternative to my buying a CD from Amazon by essentially giving me a buck or two off, they might stand to make some dough. They're getting zippo from my used purchase.

I wonder how many people are double buying now to get albums off of iTunes?