This thread again? Anyways, here's a quote from Marijuana and the Brain, Part II: The Tolerance Factor:

"Clinical studies indicate that only 10 to 20% of the available THC is transferred from a joint cigarette to the body. A pipe is better, allowing for 45% of the available THC to be consumed. A bong is a very efficient delivery system for marijuana; in ideal conditions the only THC lost is in the exhaled smoke."

So apparently there have been other studies that support the glorious bong.