"The message was written in caps over five lines that covered his belly, from his nipples to just above his genitals: I AM A SADISTIC PIG, A PERVERT AND A RAPIST."
(Larsson 208)
Lisbeth Salander gets a tattoo after her last distasteful encounter with Bjurman. On her ankle, she gets a band tattoo to make her remember. Later, in a more favorable encounter with him. she pins him down and tattoos him to mark him for what he was.
Tattoos are commonly used for this as well. Native Americans use tattoos to represent the tribe they come from. Religious sects use tattoos as a show of their faith. People also use tattoos to represent their family members. Of course there are darker reasons to having tattoos.
Gang members use tattoos to show what gang they represent. In prisons, a tear drops tattoo is used to show the number of murders they've committed. Many tattoos are used to brand the wearers, not too much different from the way Lisbeth branded Bjurman.