Apple accounts are free. You can't use iTunes with a free account or get the premium developer offerings (i.e. iOS developer certs) but you don't need to pay to use the OS or get updates.
Apple's walled garden approach to everything makes apple one of the worst offenders with regards to not just privacy, but freedom as well.
From other comments, it sounds like I can dance around to make it possible on OsX, but every other OS (except ebooks?) that I have ever installed either makes opt out a transparent (though smaller button/font) process or has no registration process at all.
I don't like that the machine will be in a very small group of opt-out OsX systems compared to reasonable percentages of other Oses. By not sharing my personal details, I might be risking my coworkers having lower than normal privacy when using OsX machines.