Read again: he includes a hidden field for the "normal" user (blind or not) and spambots fill that field out anyway and get caught. Pretty clever, but not hard to work around as a spammer if this get widely adopted.

Blind users would have a different sort of HTML rendering mechanisms (screen readers, braille output, OCR, etc) that might make hidden tags visible input unless you somehow indicated to them that the field was a honeypot. I'm not sure on the details, but the concept of hiding a field from the user's view probably doesn't translate very well once you leave the visual rendering arena.

I can't speak authoritatively, but I believe the "hidden" attribute of a field is not a visual cue, it is a presentational cue. In other words, it hides it from all presentations, whether visual, audible, tactile, or other.

"Please leave this field blank:" probably works wonders. Visually impaired users aren't mentally impaired, regardless of what the Upright Citizen's Brigade has taught you.