I got my laptop out and loaded it up while they started at me impatiently. Eventually I found the email with the e-ticket (without images) and they barely took one glance at it before sending me on my way (I think I was holding the queue up waiting for my laptop to boot).

You can always, always fake one. And put it on your computer. And take your time showing it to them. They'll wave you through eventually.

That was on a flight from malaysia. When I entered HK from China and Macau, they didn't say anything.