I have read that it gives you more of a body buzz, as the smoke seems to just stay in the lower stomach and upper intestines, where it is slowly absorbed. Less of the cannabinoids go directly to the brain (as where normally just passing through the lung membrane, straight to brain) thus contributing to the body buzz. There might possibly be tars and other chemicals deposited in the lower stomach/ upper intestines, but prolly no worse than what gets in the lungs, perhaps... although when swallowing smoke, it does stay in your body longer...
hope that helps