Blah my ex and i were 'friends with benefits' for a while after we broke up, it was fun and dandy at first until you realize it's your ex and it could always happen that because its your ex your feelings for them could pop right up again even if you don't necessarily want them to. it's risky but if the both of you are <i.positive</> that you won't have any feelings for one another if you do it then i say go for it big shooter
