If it has, we'll pause and show what we find. Insert scary scenario here; we could do this invisibly and do what we like with what we get.
If we get to Z and nothing happens, you haven't filled out a form requesting your e-mail address with an input named
email@example.com and hit Enter to reload the page.
A variant of this attack works on IE6 and IE7 by hitting the down-arrow twice and then Enter; it's much faster (and scarier) than this.
If you have not done so already, in Safari:Preferences:AutoFill, turn everything off.