Or does GM? I'm not referring here to leasing vs. buying. I am referring to the fact that GM has recently declared that only mechanics they license are allowed to work on "your" car. And if you take it to another mechanic, or use less-expensive after-market parts, or connect the car's diagnostic port to a home-brew or third-party device, the issue is not merely the possibility of voiding the warranty. The issue is, GM can more or less unilaterally declare you to be in violation of the Anti-Circumvention provisions of the Digital Millennium Copyright Act (DMCA). You can be charged with a crime at the Federal level.
Here is where the evils of DRM (that I started to write about here) intersect with the entertainment industry lobbyists' power to get stuff enacted into laws, and affect how we can use technology we think we own. These laws have effects on our lives that are not at all well-understood, not even by the content-industry monopolists who paid to have them enacted.
Do farmers own their tractors? According to comments filed by John Deere with the Copyright Office, they do not. They are not allowed to modify any aspect of "their" tractor that is mediated by software, which is pretty much anything useful. This article in Wired brings up a case of a farmer -- a neighbor of the author -- who cannot get his transplanter fixed because he is not given access to the correct diagnostic software. And so he has a six-figure barn ornament.
In their comments in support of this policy, Deere points out that if they were allowed to tinker with the tractors' software, farmers might change the engine tuning to violate the EPA pollution regulations. Well, OK, but then they would owe the EPA a fine, not John Deere. They might even use the in-cab entertainment system to pirate music. (Roll that around in your brain for a minute.) Yes, that's why the farmer spends half a million bucks on a harvester -- to evade paying $9.99 for a Taylor Swift CD.