I'm a dog lover, but haven't had a dog since DH and I got together 20 years ago as we both work FT and are out of the house 9 hours a day. But when I was a teen and my mum only worked PT our golden retriever was not even allowed upstairs never mind in our bed. Good call, because he shed like a bastard. He also occasionally ate his own poo & vomit, liked to er, pleasure himself regularly, and as he never learned to brush his teeth every night after all that activitiy he would definitely not have made a good bedfellow. 
That's not even allowing for the odd case of fleas and nocturnal diarhhoea as he got older.
We used to sit on the floor with him instead and he used to climb on our knee for cuddles and sprawl across, as much as he could being so big, anyway. Golden retriever elbows are quite sharp.
It's not hygienic, whatever people say. Dog bedding smells unless you wash it daily, so unless you like to wash your duvet and bedding daily, your bed will also smell of dog.
Plus, the thought of a dog being around while I'm getting frisky with DH is just bloody weird. Not to mention when my children were in with us as newborns. Dog owners are told time and again not to leave a dog unattended in the same room as a baby, no matter how trustworthy you think it is, but that's essentially what you're doing if you're fast asleep for hours with a baby and a dog in the same room.