Rob asks:
> Suppose there was a way to place an intercept on the Web data stream,
> perhaps on routers or switches along the transmission path.

These comments should of course be preceded by the "IANAL" disclaimer
(I Am Not A Lawyer), though personally I've always felt that the sense
of that acronym is backwards.

> Would this be illegal?

God only knows.  Why don't you try it and let us know what happens to
you :-)

> Given the borderless nature of the Internet, who could possibly
> regulate and prevent this activity?

Regulation is tough, I think, because of the international nature of
the net.

Prevention is easy.  If someone started doing this, the whole world
would switch to end-to-end authentication on all web transactions so
fast it would make your head spin.  There are easy technical solutions
(the existing SSL protocols being one of them) that would prevent people
from doing this sort of thing.

G.