I don't like the idea of marking a person as your personal property or territory. I don't like the idea of jewelry (promise, engagement, wedding, necklace, whatever), visible hickeys, lipstick marks, PDA, etc. If you can't trust your S.O. to take responsibility in making it known when necessary that s/he's taken, then why are you dating her/him?
I think these are as tasteless as
visible thongs.