I've seen a few people do this; I don't recall who I saw do it first, or which time I decided to try it myself.
( the map )Not, I think, a terribly impressive list of states, all told. Especially after subtracting the states I've merely driven through at high speed. But it does look more impressive this way than if I were to only colour in, say, the individual counties I've visited -- some of the states I've been to, I've only seen narrow slices of.