Aren't we to the point yet that if you see a page with next to no content it's pretty much assumed to start scrolling? Not to mention the fact that most people use browsers that display the scroll bar..
Sure, most people probably do, but Lion & Mountain Lion hide the scroll bar if there's a trackpad, as was the case for me. I clicked the link from pg's Twitter feed, read the words "Airbnb is poised to bring memorable local experiences to our truly global community", thought "that's nice", and went along my way.
I switch back and forth between a crappy desktop PC at work and a nice desktop PC/Macbook Air at home so I'm familiar with Apple thinking it's a good idea to hide scroll bars. That always bothered me.
It is a good idea to hide scroll bars. Saves valuable screen real estate.
Attaching a mouse re-enables scroll bars, I finally figured out.
I think most people just assume there is broken Javascript or something.