this horrifies me
I can't put it any other way.
I am a full-time Web developer who just today wasted over an hour because Sfari decided to stop submitting forms that are marked as multipart/form-data, while Camino, IE and Firefox were fine.
I also have been bitten by the iTunes freezing problems from time to time that freeze the entire OS (something that is not supposed to be possible in OS X). This has gotten considerable mention on Apple's discussion boards, with hundreds of replies.
Further, iChat in earlier iterations wouldn't save file downloads to folders named with Unicode characters.
The list goes on and on.
Centralizing things like this just makes you ask for problems. One nasty bug in WebCore, for example, will be able to bring down several apps at once...or even the entire OS.
And yes, as someone pointed out, this is the kind of sleazy **** Microsoft was pulling a few years back. Apple has already started down that road by not allowing you to set your default Web browser from inside System Preferences (in Panther). You have to launch Safari, and select "Preferences" to change your default browser to Firefox!
Ugh. I sure hope this rumor is bogus.