>> Now, suppose the TLAs have some lovely algorithm that can beat 3DES,
>> but only if they have a gigabyte or two of probable plaintext.
>> Further suppose that They really want *you*.

>not a Stallman variant. :-)  Besides, for what it would cost them to
>black-bag my place and plant that sort of deep hack in my computers,
>they might even be able to just buy me.  (I don't know whether I'd sell
>out or not...but I'm not sure I wouldn't.)

Let's not forget the good old rubber hose.  
Since to make any of this interesting, "they" have physical access to
your site - so they can just put a bag over your head and "go for it".
Much cheaper and more practical :-)

--sjg