I asked this question before, or one like it in a thread. HERE
The general I think the consensus is that pork butts don't need a lot of help since there is so much marbled fat. A cut like pork loin, however, because it's so lean could benefit from a brine more. This (IMO) is the reason that poultry benefits so much from brining. A HAM is brined (read: cured) in a solution and this helps with moisture and flavor, but can give it a salty taste (salt cured ham....) but they are done for a very long time I believe.
is a recipe where Alton Brown brined and smoked a pork butt. If there's one person I trust knows more than most about the science of food, it's AB.
The best thing I can offer is to try it out and cook a side-by-side to see if there's a benefit. Just make sure you let us know!!!!