Personally, I find it repellent when people let dogs lick the plates humans eat off of. I am allergic to dogs, so it is especially bad for me. I know that the plates get washed, and so theoretically all traces of the dog saliva which is in allergen irritant should be gone but it still rankles me. I also think it is bad for the dog. Letting the dog lick a human plate of food exposes them to many types of foods they cannot digest such as garlic, which is in many sauces. Plate licking also encourages the dog to have a seat at the table, so to speak, which encourages begging. Nothing is quite so unpleasant in a meal as having a dog stare at you, waiting for the plate to drop to the floor for their meal time. I find the practice so poor, that if I visit your home and your dog eats off the plate I will actually bring my own dishes and silverware the next time I eat at your house. It's actually caused some problems with my parents who frequently let the dog sit at the table and lick their plates. Ultimately it's your decision, but if you consider your dog part of the family I consider plate licking bad parenting.