I definitely wouldn't do it with 2 adult couples, even if the other couple was my child & his/her spouse. IMO, the sofa bed isn't good enough for two (unless they are children), plus there would be very little privacy. (I would hate being "trapped" in the bedroom, especially later in the evening or early in the morning. I need my morning coffee!!!).
But that's me - it really boils down to the individuals involved.