The main sources of toxoplasmosis are from raw meat and can be passed to humans that way. If the dog has eaten something that is infected by toxoplasmosis which has not been eradicated in cooking, it will remain live in the dog faeces - as will salmonella, listeria, e-coli, campylobacter and so on. Because dogs digest their food more quickly, as their digestive tract is shorter they may not necessarily suffer from infection (there is always a chance they will though). These and other parasites are excreted live by the dog and theoretically pose a risk of infection. Now some may argue that the risk is minimal but these are serious infections that in children, the elderly and immunologically compromised (people on chemo and so on) could be life threatening. Dogs are not the cleanest species on earth and pooh can get carried into the house and so on their paws, fur or chidlrens feet and so on. There is no data to say if this is not a real problem, but infections have been reported in dogs.
I know some people don't support this as being a risk - but it is always there and therefore needs to be considered. If cats are a risk, theoretically so are raw fed dogs.
I just know I am going to regret posting this - I have been trying not to cause an argument. By the way I am a nurse, which is maybe why I am so paranoid. Who knows?