I just placed an order for my third Mac ever, this time a new iMac. I realized my 2.5 year old powerbook wasn't worth upgrading if they'll go to intel someday, and I was just using it as a desktop 99% of the time so I might as well get something designed to sit on my desk instead of my lap. Another odd tidbit is that four years ago, I used to build computers from whatever motherboard was on sale at Frys, and now I buy pre-built non-upgradeable computers. Funny how that works.
Anyway, my point is iTunes and the "renting" problem with their music. They went from allowing three machines to five after Cory at BoingBoing complained, but I think I have a better solution.
Now that I'm on my third bit of hardware, and I've had a hard drive crash on the first powerbook, and I've given my wife copies of some songs, I'm pretty sure I've exhausted five machines for some tracks. But when I get my new machine and I register it, Apple will know it's me. They own the hardware, software, and servers that both the new computer registrations and music store purchases go through. Why not connect the two? The solution to the number of machines problem is an easy one.
Instead of allowing three machines or five machines to unlock a iTunes song DRM, make it n+1 where n equals the number of Macs you have purchased and registered. It does two things for you that are both good for Apple and good for customers. One, it lets people know their iTunes music has a future. If I buy a song today, and I buy a new mac each year or two, I'll know that ten years down the line the file will still play (and this isn't a total stretch -- I have mp3s from 1997 saved somewhere). The other thing it will do is remove any hesitation to buy a new Mac on the part of your customers. Imagine if I had purchased hundreds of songs (I'm probably somewhere close to that). If you could ensure that my purchased music collection can follow me from mac to mac to mac, I'd be a happier customer of both your hardware and music services.
Think about it, (n+1) is all I'm asking for here.