One of the more interesting problems I've encountered with the Vive is. . . What happens when you push your face into a wall?
First I have to say, this is *extremely* counter-intuitive to do at first. Pushing my face into a wall really doesn't come naturally at all.
In some games (or not-exactly-games, like realities.io) you can see what's on the other side of the wall, and you can get glimpses of things you aren't really meant to see -- which can be fun and useful. In other games the display just fades to black, preventing you from "cheating" in this way.
A few days ago I got Compound, which is a simple-but-addictive demo game, where pushing my head into a wall moves the wall. Actually, it moves EVERYTHING. It just nudges the whole virtual world over a few inches. Which is odd, but oddly cool. If I get too close to a *real* wall, I can always step back to the center of my game space, even if it looks like there's a virtual wall in my way.