re: I think this becomes noticable when you use a Vista machine.
Latterday updates to IE under any OS added the warning about script copying stuff to the clipboard. I can understand limiting script access to the clipboard in general as a privacy feature, because a Web page could lift info from the clipboard then send it to a server. I used that technique when I was playing with a Nigerian scammer, and one time picked up a couple of dozen addresses of people he'd just sent his scam letter to. You never know what might be sitting on your clipboard when you browse the Web, and on balance it's a good thing to warn you about access either copying or pasting.