That's because it is for use in Japanese, not the US - http://en.wikipedia.org/wiki/AC_power_plugs_and_sockets#JIS_C_8303.2C_Class_II_unearthedWould you install these? I wouldn't, and here is why:
- No place for grounding prong for three-prong cords
- Too easy for multiple line-line/neutral-neutral/line-neutral shorts, especially on the vertical runs
- Existing solutions to the problem it purports to solve without introducing new dangers (such as this squid outlet multiplier)
- Doesn't appear to be tamper-resistant
I cannot see this getting UL approval without at least a modification to add in a row for grounding prongs.