Good point. My javascript solution uses two hidden fields with very similar names. One that the script fills in and one that it doesn't.
Bots will either hit both or neither and get rejected. Screen readers/toolbars may be an issue, though the names would be hard to think what to autofill with. It has never come up in practice -- the reject message tells people to email us directly
If you have javascript turned off, you'll need to email directly too -- and the site won't work so there probably isn't much lost!
