There are plenty of cases where children have stuck things in outlets, which is why these things are sold:
![](http://trus.imageg.net/graphics/product_images/pG01-3728221dt.jpg)
That said, almost all of the AC shocks I've experienced haben't paused tooo buch brain dablage.
![Cheesy :D](https://www.eevblog.com/forum/Smileys/default/xcheesy.gif.pagespeed.ic.KPzuH4J-TG.png)
Nah, seriously, it tickles or hums a bit, but that's when I'm not creating a low-impedance path to ground with another part of my body, either. Now, take a small child, and it'd be easily possible for them to take a metal object in one hand, place their other hand on a grounded object, and stick that metal into the hot side of the socket. I shouldn't have to tell you any more.
IN MY VIEW, no system is inherently dangerous or safe. It's almost always the humans involved that make it so. Here in the US, those plastic outlet plugs are just one of those things expecting parents buy (or at least, intelligent ones do), and it's one of a boatload of things they do to keep their children safe.
As for the "which way is up", I personally let the face plate determine it. If it's metal, the ground pin goes up, because if the metal plate somehow happens to fall forward (off the junction box, due to a stripped screw or mischievous morons), and something is plugged into the outlet, the plate won't become hot. Instead it will rest on or hit the ground pin FIRST, instead of the chance of resting on the hot blade. This is how ALL of the outlets on my lab bench are set up, and in some cases, it's allowed for easier cable routing -- many of my power surge suppression strips and instruments have molded, angled plugs.
I'd suggest finding a copy of the NEC handbook, reading it, and understanding it, before thinking that any of the modern US electrical systems are 'dangerous'.
EDIT: 120V is just a nominal value; 125, 115, and 110 VAC are sometimes quoted, too. It's almost always 123.4 VAC at my apartment, but anywhere between 112 and 124 VAC at my parents' place across the state. And just because I'm lazy, look at this:
Voltage levels
All of Europe, Africa, Asia, Australia, New Zealand and most of South America use a supply that is within 6% of 230 V, whereas Japan, Taiwan, North America and some parts of northern South America use a voltage between 100 and 127 V. The 230 V standard has become the most widespread so standard 230 V equipment can be used in most parts of the world with the aid of an adapter or a change to the equipment's connection plug for the specific country.
Measuring voltage
A distinction should be made between the voltage at the point of supply (nominal system voltage) and the voltage rating of the equipment (utilization voltage). Typically the utilization voltage is 3% to 5% lower than the nominal system voltage; for example, a nominal 208 V supply system will be connected to motors with "200 V" on their nameplates. This allows for the voltage drop between equipment and supply. Voltages in this article are the nominal supply voltages and equipment used on these systems will carry slightly lower nameplate voltages.
Power distribution system voltage is nearly sinusoidal in nature. Voltages are expressed as root mean square (RMS) voltage. Voltage tolerances are for steady-state operation. Momentary heavy loads, or switching operations in the power distribution network, may cause short-term deviations out of the tolerance band. In general, power supplies derived from large networks with many sources are more stable than those supplied to an isolated community with perhaps only a single generator.