Quote: Nogget @ January 5 2012, 1:11 PM GMTWas it really necessary for Adler to keep allowing her phone to leave her possession, if it was her only insurance? I'd have kept it in a safe place and copied the code-which-need-deciphering into some other phone, then sent that to Sherlock.
I think you're concentrating too much on the MacGuffin, the phone could have just as easily been an amulet or a treasure map - it was there to drive the plot forward.
But if you want to look at it logically - giving the phone to Sherlock provided additional insurance, meaning that even she was captured / killed, the evidence on her phone could still get out there.
Secondly, if Sherlock couldn't crack the code to her phone, then no one could, thus sending out the message that if terrorists want the info, Adler has to be alive to access it.
Thirdly, if she'd sent a fake phone to Sherlock, he would have noticed. He can look at a lapel and know how many dogs you own, etc.