Such a structure consumes a scarce resource -- creative effort -- wastefully, and restricts an abundant resource -- communicability of information -- unnecessarily. That seems very much the opposite of economically efficient.
Information goods should be more like better kinds of software production. But the current copyright-based system makes it all more like a 'waterfall economy'
The "isn't worth it" actually goes the other way at this point: it's isn't worth pirating anything you can get from iTunes. Most of their customers are perfectly capable of pirating stuff, but it isn't worth their time compared to grabbing it from iTunes.
I'm not saying nobody will ever compete with them or that people don't still pirate anyhow, just that they're more than capable of competing with free. They've been successfully doing that the entire time, in fact.
That's exactly the part that makes me believe they have staying power.
What's really happening is that, the easier piracy becomes, the closer the supply curve comes to turning into a very flat line at price 0. Now, the actual cost to the consumer in time, energy, bandwidth, and guilt is higher than 0, and it's possible to reduce those costs by trading off some actual money cost to get the permission of copyright holders the way Apple or Rdio are doing, but it's not clear that this will last forever.