Piracy is an interesting topic. There's no telling with every digital copy of something if it's genuine I'm taking this because I can, or if there's some other reason behind it.
Does every pirated copy translate into a lost sale? No, of course not. Sometimes people pirate things because it's the only way to get it, at least in the short term.
Sometimes being stranded in a foreign country that's pretty much a prison with little entertainment other than the internet will do odd things to people. Sometimes if they're stuck in a place where the primary method to get a movie is to pirate it, they'll pirate it, watch it a few times, then delete it. Other times they'll keep it, swap around a few movies, come back to civilization, and then buy actual copies. Sometimes they pirate stuff because it's more convenient or faster than doing it legally(Yes, it sounds weird, but a CD-Rom can only be encoded into a music format at specific speeds, which are now slower than the internet).
Sometimes they'll pirate stuff simply because it can't be gotten at reasonable prices from a retailer, because the producers went out of business, or stopped producing a product line(Yes AEG, I'm talking about 7th Sea).
Sometimes piracy can generate sales. If a company did it right, they could use piracy to their advantage, as a tool, instead of just throwing a tantrum at trying to fight it tooth and nail.