Pacifier

yep, with very high frequencys the electric current only travels at the surfance of the conductor. This is called the "skin effect"
You can even play "magician" by using your body as a conductor for very high voltages:
http://www.ucsc.edu/currents/00-01/a...-10-30.155.jpg
he only survives because of the high frequency.

As for the efficiency, since you have higher voltage you need lower current therfore you can use thinner conductors. Also the loss when tranfering power over a longer distance is lower when transferes whith higher voltage. Here in Germany transmission lines (http://www.zoll-d.de/z1_bilder/a1_vst/strommast.jpeg) uses up to 360 000 Volt

The reason why the USA uses 110V and EU uses 230V are a bit unclear. From what I know at the beginning the first arc lamp used 55V. But that wasn't enough for long so it was doubled. in the USA they thought 110V was enough, in the europe the even quadrupled it. Perhaps it was because in Europe there was a shortage of copper during WW1 and they prefered to keep the conductions as thin as possible, in the USA they decided to live with the higher losses and just build more transformers.

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"It seems to me that the idea of a personal God is an anthropological concept which I cannot take seriously. I also cannot imagine some will or goal outside the human sphere. Science has been charged with undermining morality, but the charge is unjust. A man's ethical behavior should be based effectually on sympathy, education, and social ties and needs; no religious basis is necessary. Man would indeed be in a poor way if he had to be restrained by fear of punishment and hope of reward after death
— Albert Einstein