The latest iPods have a cryptographic "checksum" in their song databases that prevents third-party applications from synching with the portable music players. This means that iPods can no longer be used with operating systems where iTunes doesn't exist — like Linux, where gtkpod and Amarok are common free tools used by iPod owners to load their players.
Notice that this has nothing to do with piracy — this is about Apple limiting the choices available to people who buy their iPod hardware. I kept my iPod when I switched to Ubuntu Linux a year ago, and I've been using it happily with my machine ever since (though it took me a solid week to get all my DRMed Audible audiobooks out of iTunes — I had to run two machines 24/7, playing hundreds of hours of audio through a program called AudioHijack, to remove the DRM from my collection, which had cost me thousands of dollars to build). I'd considered buying another iPod when this one started to show its age — it's a perfectly nice player to use, provided you stay away from the DRM.
The new hardware limits the number of potential customers for Apple's products, adding engineering cost to a device in order to reduce its functionality. It's hard to understand why Apple would do this, but the most likely explanations are that Apple wants to be sure that competitors can't build their own players to load up iPods — now that half of the major labels have gone DRM free, it's conceivable that we'd get a Rhapsody or Amazon player that automatically loaded the non-DRM tracks they sold you on your iPod (again, note that this has nothing to do with preventing piracy — this is about preventing competition with the iTunes Store).
It won't be the first time Apple has rejigged iTunes/iPod to lock out competitors: back when Real built a DRM player for its own music that would run on an iPod, Apple threatened to sue them and engineered a firmware update to break their code (again, nothing to do with fighting piracy). This is the soul of anti-competitiveness: Real made code that iPod owners could use to get more legal use out of their iPods, Apple threatened to sue them for endangering their monopoly over delivering iPod software.
This is all par for the course, of course. Businesses have taken countermeasures to prevent competitors from interoperating with their products for decades. Apple had to break Microsoft's file-formats to give Numbers, Pages and Keynote the ability to read Office files — they're enthusiastic participants in "adversarial compatibility." Decades ago, IBM lost a high-profile lawsuit against competitors who'd been making compatible mainframe accessories and selling them for less than IBM, wrecking IBM's business-model of selling cheap mainframes and charging a fortune for accessories. The law of the land has generally been that compatibility is legal, even if it undermines your profitability — making a product does not create a monopoly over everything that your customers might do with that product.
That was then. Now, Apple has the Digital Millennium Copyright Act on its side, which makes it illegal to "circumvent an effective means of access control" — that is, to break DRM. I don't know if Apple will invoke the DMCA against people who break this latest measure (they threatened Real with the DMCA before) but I guarantee you that the attorneys and investors advising potential iTunes competitors are going to be very conservative about this. The upshot is that iPod owners and the public interest lose out, because competitive products that expand the utility of the iPod are less likely to come into existence, thanks to the DMCA and Apple's locking technology.
I guess my next player won't be an iPod after all.
With the release of the new range of iPods – the new Nano, the iPod Classic and the iPod Touch, we were expecting more of the same – a few tweaks here and there and everything would be fine. No so.
At the very start of the database, a couple of what appear to be SHA1 hashes have been inserted which appear to lock the iTunes database to one particular iPod and prevent any modification of the database file. If you try to do either of these, the hashes will not match and the iPod will report that it contains "0 songs" when the iTunesDB would otherwise be perfectly adequate.