While working with Chinese symbol tattoos, sometimes I have come across mistakes which have been tattooed onto people's skin. At the same time, the person who has the tattoo on his arm or back is often unaware of what the Chinese symbols mean or in what way are they incorrect.
For example, a lady in tears showed me her tattoo which said "free" in Chinese. She just learned that this particular "free" means "free of charge" and has nothing to do with "freedom." There is no reason why a woman should wear the sign "free of charge" on her skin and it is quite embarrassing. In Chinese, the two concepts have nothing to do with each other: one is pronounced ziyou and the other mianfei. But if you go to a Chinese restaurant and ask a waiter to write you down the word "free" in Chinese, he might not realize that you need this for a tattoo and would write the words "free of charge." If you need a tattoo design, go to a designated service.
A much more common mistake is that the Chinese symbol is flipped horizontally and thus is a mirror image of what it should be. I think this might be the problem when people use temporary tattoos or work from those because after a while you might get confused as to which side is the correct one. To have a Chinese symbol tattooed on you backwards is also embarrassing.