I was going to mention this last night, but I'm lacking in motivation as of late, so Tam beat me to it.
In the handful of places I've seen mention of this story, it never fails that one of the first comments is in regards to how dumb of an idea it is.
I completely agree.
I don't care how much you publicize the "virtual speed-bumps," there's still a percentage of people who won't have heard about it, and could conceivably swerve into oncoming traffic to avoid hitting little Suzie.
There's another percentage that will no doubt be driving that same route every day, and that's where the post's title comes from. It's a long standing saying in the military. Don't get used to things, or you'll wind up dead; don't let your guard down; etc... In this case there's a chance that one of those regular commuters will become so accustom to "running over a little girl" on the way to work that if a kid did chase a ball onto the road in the area that driver's not going to think twice until the telltale "thump."
The forced perspective aspect is kind of cool, but the anthropomorphizing of the image is equal parts morbid, tasteless, and dangerous. Why not just a giant 3-D "SLOW DOWN"?