Those are pretty fun, but messy.
The effect is so easy to do with the right kind of shot, that most people just don’t pay enough attention to the focal plane that would make the image 100% believable.

Not that anyone else would notice.
I’m just way anal.

OK, we get it, you can blur the foreground and the background using photoshop to make things look like they’ve been miniaturized. This has about as much staying power as the discovery of the gaussian blur filter.