I think it's really stupid when somebody completely blacks out there tail lights. A couple of coats is fine but there is a fine line between safety and "coolness". Personally I like a pretty light smoke and not a fully black light.
In Michigan it's legal as long as you can see the lights from a couple hundred feet. 500 I think, but don't quote me. You have to use a lot of common sense and courtesy in a situation like this and unfortunately a lot of people are dumb and don't think about it.
2003 SVT focus
Build number: 61 of 3985
Assembled January 23, 2003