Chris Lewis wrote:
According to Al Bundy :
You don't screw it in. You nail it with galv roofing nails.

Your reference also mentioned screws.

Why wouldn't you use screws?

I use 2 1/2" #8 deck screws, no predrill. That may be overkill, but the
subfloors NEVER move, they wouldn't dare ;-)

You can do that with hardibacker? Deck screws would be impossible.
Even self countersinking screws have a hard time with it.

http://www.ontariotile.com/cbuhardibacker.html