[dionidium]

The latest National Electric Code requires tamper-proof receptacles practically everywhere. See: https://diy.stackexchange.com/questions/13414/are-there-loca...

I guess they wouldn't entirely eliminate this specific problem -- if you were determined to get a plug in halfway and touch one end with a penny, then you could probably pull it off -- but they do make unintentional errors of this variety much less likely.

I replaced all my receptacles with TR versions when I moved in to this house. It takes an afternoon, but it's a good opportunity to make sure they're wired correctly -- you may be surprised to learn that many won't be -- and to replace old, worn-out outlets that present hazards. It's a very easy job for a homeowner, given some basic knowledge about residential wiring that's easily obtained.

[Grazester]

The receptacle is only part of the problem.

On 220uk plugs the part of the pins that is partially exposed as you insert the plug is insulted to prevent people doing stupid things like this coin thing.