People like to point to the guy on top as big and evil. Rightnow it's Apple, 12-15 years ago it was Microsoft. Tomorrow it could be Google.
The iTunes cracking restrictions are probably related to their contracts with providers selling stuff on the iTunes store. The requirement to use iTunes for managing iOS devices is simply because no other software has been written to do it.
There's no documented requirement to only use Mac OS X for iOS development. Infinity Blade (seen here on the left: http://www.apple.com/ipad/from-the-app-store/games.html ) was mostly developed in Windows ( see http://udn.epicgames.com/Three/GettingStartediOSDevelopment.... ).
There's also very real concerns regarding hacking - i.e. you want to avoid getting the rep for being that company responsible (think Sidekick) for the Paris Hilton situation, where all of hollywood's A-list celebrities phone numbers get leaked onto the internet. You're trying to build a secure device.
The business motivations are obvious. Apple builds a good closed system. Google builds a janky open system. Both models work, neither is right or wrong, and both companys go to the bank.
And just to put things into perspective, there was no App Store when Apple launched the iphone. I'm pretty sure they never intended for there to be, but once they saw what people were coming up with 'off the ranch' it became fairly obvious to them to let developers develop on their platform. The reason I'm fairly certain Apple had no initial plans for this is simply because, on the version of the first public firmware (and only the first one), everything ran as root user... that's just idiotic.
What about Psystar?
As for Psystar, what about them? Apple has not gone after the hackers who figure out how to run OS X on non-Mac hardware. They've not gone after the numerous web sites that tell you how to do it. They've not gone after the book you can readily buy at B&N or Amazon on building a hackintosh. They've mostly looked the other way (hell, they have even been known to include in OS X updates bug fixes for problems that only manifested themselves on non-Apple hardware). It sure doesn't look like Apple has much of a problem with people hacking.
Taking an existing idea and implementing it far better than the incumbent is not ripping off. It's progress.
Ripping off involves wholesale copying without adding anything original, substantial, or worthwhile to the effort.
It's more like a great indy iPhone app that increases the value of the phone and even becomes one of the reasons people are buying the phone. Then Apple decides to build the same functionality right into the phone making the app obsolete. That's a much better analogy.
Now I'm not against Apple doing that at all. In fact I think it's a no-brainer, and failing to do it would be disappointing. It's just a shame that the little indy guys who created that market for them get shut out. Toss them a couple million bucks or something you know?