"If I go to target, slip a copy of Harry Potter V into my jacket, and walk out [...] If I come home, open up Limewire, and download it [...] It's the same exact thing."
Absolutely NOT. A good analogy would be that downloading a book online and printing it out is akin to finding a copy in a library and photocopying it.
When you steal it from the book store, you are *taking away* their copy. For instance, if the book store paid $15 for a book that they sell you $25, and you steal that book, the store loses $15. They've also lost a potential $10 profit, but it's not a definitive loss. No one can say for sure they would have sold that book. Maybe it would've just gathered dust on their shelves.
On the other hand, when you download the book, you're *copying* someone's book, meaning that they get to keep their own. No one loses money in the transaction, but like the book store lost the potential $10 profit, the book's publisher lost a *potential* sale. It's not a definitive loss: if downloading wasn't available, does that mean that people who have downloaded it automatically buy the material? Of course not. Most would simply opt to do without.
Take Photoshop, for instance. A vast majority of people who use Photoshop recreationally (ie, not for business purposes) pirate it. If pirating Photoshop wasn't possible, non-business users still wouldn't buy it, because it costs too much. People would simply use another graphic software, like the GIMP, which is free (legally so). And if Microsoft ever comes up with a perfect, unbreakable way to insure that pirated copies of Windows can't run, you'll start seeing a lot more computers running Linux, let me tell you.