Many thanks to those who provided their feedback about our little biscuity and apple-flavoured friend.
The method I am currently using to feel that I have shown due diligence to my all-important privacy, without having to do a double sign-in for iTunes, is long-winded. I will continue to nag Apple on the Developer's Bug Report pages but perhaps those who agree with my findings can do the same at the normal feedback links here:
http://www.apple.com/feedback/itunesapp.html
and/or here:
http://www.apple.com/feedback/safari.html
For anyone that can stay awake long enough to get to the end, this is how I currently clear Safari in a way that retains my iTunes login:
This is for Mac users only I'm afraid.
Reset Safari with 'Remove all website data' UNCHECKED
(Safari will reset, and then it will open your usual Homepage afresh).
Go to Safari, Preferences, Privacy, Details
(this is the list of all the nasties (and goodies) that your surfing has Dyson-ed up on its travels).
Select all of the items
(I click on the first item on the list and then use SHIFT+ALT+DOWN ARROW, but you may have your own method).
Deselect 'apple.com'
(I use CMD+LEFT CLICK)
Now select 'Remove' (NOT 'Remove All' of course)
(Wait a few seconds to allow the deletion to completely finish. I find that 'apple.com' will disappear after a moment and when it reappears it should be OK to select 'Done' to close the window. If you've closed it too quickly you might see the odd item creep back in; no biggy, just do it again).
Close Preferences and close Safari.
Do keep in mind that your usual Homepage will have immediately thrown its own cookies straight back into Safari; it's nigh on impossible to have a completely empty cookie cache.
I often then run Michaël Fortin's excellent Black Hole (available for free at Irradiated.net or Mac App Store) which allows you to target anything that Safari's reset doesn't clear, and much more besides.
Disclaimer: I have no affiliation whatsoever to Black Hole or its developer, and other equally splendid privacy applications are no doubt widely available!
Clearly this is all ridiculous.
I've already mentioned one seemingly simple solution in my previous post, which is to have the specific 'iTunes/apple.com' cookie stored elsewhere (perhaps within the iTunes preference folder, or am I just being incredibly stupid and/or naive!?).
A second solution would be for Apple to finally give Safari users an infinitely more useful privacy menu/checklist that allows us to decide which cookies should persist and which should be flushed when "Remove all website data' is used.
Gnail mentioned Piriform's excellent CCleaner (available for free at piriform.com or Mac App Store) which handles this very issue and has also recently become available for Mac users. I swear by it for Windows but I've yet to try it myself for Mac because Safari seems just a hair's breadth from having such a feature available. I always prefer an integral solution over a third party one wherever possible anyway (no disrepect at all to the wonderful third party developers doing such a terrific job out there).
Disclaimer: I have no affiliation whatsoever to CCleaner or its developer, and you now have proof that other equally splendid privacy applications are available just like I told you!
So: GO ON APPLE! You've got the list there, all the cookies and details are there, so all we need is to be able to check or uncheck them and you'll have a much happier bunch of iTunes AND Safari users - it's a Win/Win surely!?
Apple don't necessarily read this forum so we can all file our Enhancement Requests here: http://www.apple.com/feedback/safari.html if we want to.
Huge apologies as ever to Skiziks for my equally huge interruptions on this thread.