Dating ex prisoners
Any two party relationship--employer-employee, priest-penitent, lawyer-client--implies a prisoner's dilemma. A failure to make a sacrifice in return, a dishonesty or infidelity, is a defection. Making a sacrifice for someone you love is playing the cooperation card.
Tolstoy pointed out in "Family Happiness" and many others have also perceived that there is a serious distinction between being in love and loving.
If I live with you, I want a ring within a certain period of time, may be translated as, if I play the cooperation card, how do I know that you will do the same?