Friends with benefits is ok.... But there's a fine line.
E.g. I have a 'friend' who was with this guy for a couple of weeks, they fucked, he asked her what they were after that, she told him he was a mate, that the friends with benefits thing would be cool... But they ALSO agreed that they wouldn't see anyone else, would be more or less exclusive, met the parents, cuddles and kisses.... Friends with benefits in name only, really.
Anyone who says friends with benefits means no one gets hurt ever is either retarded, or is amazingly good at keeping feelinggs out of it.