It is my opinion that the idea evolved from folks trying to get smoke flavor to meat on the grill-- probably introduced by some gas grill owning heretic.  The theory is that the water helps the wood chips/chunks smolder and not burn up.  Yes... I have found this to be true for about 30 seconds.  What is seen initially is as much steam as it is smoke and once the minuscule amount of water is driven off the wood begins to burn-- usually rapidly.  When this is done for barbecue and the wet wood is added to a smoker the real potential here is that your Q will taste like a recently extinguished house fire.  Yum!  :)  If one is smoking meat, presumably at or below 250, then the wood should not instantly burn up as there should not be enough oxygen.  If the smoker can't make that happen then there really wasn't any chance that much smoking was going to happen any way.  Further more, with the exception of stick burners--and not always then, the fire should be constructed using The Minion Method and therefore very little charcoal should be burning to ignite the wood.  This will significantly extend the burn time of the fuel as well as prolong the period of time the smoke is generated.

The choice is yours-- soak or not.  I have always chosen not.  Next week I will address the searing "seals in the juices" myth.