Personally, I think that the reason co-sleeping isn't recommended by SIDS Australia, Ngala or anywhere else "mainstream" is because it isn't 'the done thing', it's not as socially acceptable as sleeping seperately. I wonder if this is because in the bad old days, women were told right from the time their babies were born to teach them to be independant (with timed feeds, etc.). Maybe some of it is even the influence of the womens lib movement which unfortunately encouraged the same thing, encouraged women to seperate themselves from thier children and have their own lives.

Co-sleeping is safer for babies. I think manta-ray already said that mothers and babies react to each other during the night, waking each other occasionally which actually stops the baby falling into too deep a sleep and hence stop breathing. Eventually we'll all be advised to co-sleep with our babies, I think.