This commonly stated point of view is plain wrong. Apple, like all other suppliers of any product, does business in accordance with the law of the applicable jurisdiction. The law relating to the installation of OSX on white boxes is copyright, specifically Title 17, first sale, contract law, and the various sale of goods and consumer protection legislation. The question is whether Apple can simultaneously sell OSX at retail in the form of fully functioning retail copies, and also then tell the buyer on what hardware he may install it.
Psystar fell at the first fence in terms of testing this. Their method of operation breached copyright.
What they did was to buy a copy of OSX. They then installed it on a Mini. So far they were legal.
Next they modified this installed copy, which created a derivative work. Probably at this point they were borderline. If done solely for their own use, probably they would have been OK.
But they now went on to use this as a master copy to install the derivative work on other machines. Breach of copyright.
They next transferred the derivative works to customers, sometimes having included other copies of OSX than the one installed from, sometimes even failing to do that. This was also breach of copyright. Even were the modifications essential to use with the new machine, transfer of those modifications is only lawful under Title 17 if you get the consent of the copyright holder.
But this is all about Psystar's method of operation. It is not about the rights and wrongs of the matter. Whether if you install OSX on a white box, or have someone do it for you on the white box you own, and with a retail copy you own, is a quite different issue and has not been tested. It is going to turn on the issue of whether you are the owner, or the licensee. The case of Blizzard and the case of Vernor vs Autodesk are in conflict here, and the issue is moot.
If you are the owner, then contrary to the above post, your installation on the machine of your choice is protected by section 117 of Title 17. This allows you to make any adaptations and copies which are essential to use with a machine. If your copies are lawful, then circumventing protections in order to make them will also be lawful. In terms of the EULA and contract law, it is not clear that post sale restrictions on use are in fact enforceable. It is not clear, for instance, that if Apple were to put in their EULA the condition that you were forbidden to load and run Open Office on your Mac, this would be enforceable. Other conditions that are not clearly enforceable might include if MS forbade you to install Windows for dual boot on a Mac, if they forbade you to install Windows in a VM, if they forbade you to run Office under Wine.
It is a common cry of the Mac Fanatic that OSX is Apple's and they can do what they like, and if you don't like it don't buy it. But it is both false in terms of the way that business law works in the US, and it is wrong as a matter of public policy, since were it correct, it would permit wholesale anti competitive action by companies, which would have the potential for harming Apple and its customers as much as anyone. The whole intellectual pseudo problem is created by the desire of the Mac Fanatics to have one set of rules for Apple, and another for everyone else. But this is not how the law works.
Bottom line: if they sell it at retail you can install it on whatever you want. If they do not like this, it is them that has to change, and stop selling it at retail in a form which is installable on machines they do not like. And if you can do it yourself, you can pay someone to do it, as long as you own the software and hardware at the time of the work being done.