I have seen this service performed by several people in different countries. The most interesting things about it, which I think deserve to be especially pointed out, are:

1. Not only do these people draw relatively complex(or in the case of Chinese characters, very complex) lines that are only a few millimeters high, they do it on the fly, while you are waiting. Imagine programming or plumbing houses or whatever you do for a living while someone is watching and waiting.

2. I have seen people who do this but who are able to create only a subset of the alphabet, and who put up signs to that effect. This is very interesting, because it serves as a guide to the complexity of the alphabet and can also be used for a Shannon-like analysis of the distances between characters.

or something... pretty cool anyway!