Wrong direction. Approaching would show a blue shift. Red shift means it is already passed and going away. In practical terms, one might not be able to tell the difference.

Part of the reason is that several of the very earliest attempts at the scam, using standard postage, did originate from Nigeria. In the 1970's, I received a couple of them. (I worked in the petroleum industry at the time.) They were hand written and both were postage stamped from Nigeria. Over time, they have modernized their approach only slightly but still follow the basic outline. Now, it hardly matters where the email originated; they only need a story that can be made to sound credible to a few recepients in order to make it worthwhile.

In general, the sounds are not all that pleasant to live with. The make a lot more noise that most people would think until you actually get close to one or, even more, close to a whole wind farm of them. Most (but not all) people who complain about the noise of nearby trains or airports are at the disatvantage that the tracks or airport was there first. In this case, if you already have a home and someone else wants to put this unpleasant noisemaker near by, it seems that you might have some right to complain.

The reference to 10-cm is (probably unintentionally) misleading. I was thrown off at first until I went to the gismag article. The 10-cm is the length of the projectile. In the picture, the bore appears more on the order of .50 cal. This is why so many replies have referred to it as a dart.

http://www.xkcd.com/912/