Saying that crippling single user mode is an easy change to reverse is like telling someone that it's no big deal to put a first aid kit in your parachute pack, because if you decide later that you'd rather have the parachute in there it's easy enough to repack it.

That is, by the time you're in a situation where you'd care, it's too late.

At first glance, this does look like an interesting suggestion, but the other posters are right: this suggestion is paranoid to a fault, and so only suitable for certain kinds of highly locked down environments where you absolutely cannot have anyone messing with your computer and would rather lose everything on it than let someone break in.

If you're the sort of person that would burn down your own home before allowing a burglar to steal anything in it, then this hint is for you. If you're willing to cut your losses & collect on the insurance instead [or as the case may be, you've backed everything up and can clean up as necessary], then this hint is going to do *way* more harm than good for a lot of people.

Please make that risk clear, Rob.