"Piracy" exists for one reason and one reason alone: the price is too high for the consumer. There will always be a subset of the economy that will steal a particular good (i.e. for whom the price is always too high), from CD's to clothing to Ferrari's. This criminal element is simply a cost of doing business, really. In a healthy market, their costs are easily absorbed by a much larger subset that is prepared to pay the set price of the good. Match demand for the product reasonably well with supply and everyone is happy.
When a product is priced at a level that is greater than the market values, problems emerge. In open/free markets, you tend to get competition and innovation, and individual business losses. In closed/highly regulated markets, you tend to get black markets, bootlegging and all sorts of evasion if demand is high enough to warrant. This is as true for music and software as it is for gasoline, alcohol and copper wire. Music piracy is simply a black market that is only sustained because enough of the market thinks the price is too high.
The labels that have tightly controlled the market for music (commoditizing something that 50% of the population can supply) have done so by closing all distribution channels and limiting any real supply in order to exaggerate demand. Consumers didn't really know that they were being ripped off, since the supply chain was so tightly controlled. That changed with Napster.
Once the entire industry was exposed, and music began to revert back to a more natural value that one would expect for such a large supply, the market's opinion of the product began to change as well. (To be honest the shift probably went too far to the other side, but it started to regulate as things like itunes emerged)
What's evident is that there is clearly a value above zero that the market will place on music. If this wasn't the case, iTunes wouldn't be around. The problem that most labels - and sadly artists - fail realize is that the particular dollar point could be a lot lower than they would like it to be. Probably more like $.50 a song rather than the current $.99 cent price point.
The market will determine that price though, not the suppliers. Until then, major piracy will continue. Find that price point though, and piracy will go back to meaning peg legs and eye patches.