Until recently (i.e. Wallace & Grommit), the cameras used to take close up pictures of models had a very narrow depth of focus - i.e. the distance between the closest and furthest things in focus in the image.
This means that we have been programmed to expect such an effect in pictures taken of small things, close up - doesn't take long to brain wash a population, does it?
These videos, and their like, use post editing of the images (or, as pointed out, many cameras now do it too) to give this effect. Many of them also use time lapse videos which give a stop-motion effect a la 'Jason and the Argonauts'.
You can have a try with your own photos via an online editor here:
http://tiltshiftmaker.com/