Reading this thread I'm growing more confused. I only knows 2 ways and 2 reasons for marinading.
1. Imparting flavor - a quick marinade that may contain whatever ingredients you like, including salt and/or acid to give a quick flavoring component to a protein. The marinade does not soak into the meat on a deep level but more or less becomes a basting and cooks right on to the surface.
2. Tenderizing and flavoring - a long marinade containing acid but no salt. Helps to break down the tough fibers in some cuts of meat. Salt is added right before cooking in order to avoid toughening and drawing out the moisture of the meat.
I once marinaded chunks of leg of lamb for kabobs. The marinade was yogurt, lemon, pepper, saffron, onion, garlic, & olive oil and I kept them in there over night. Trying to skewer them the next day was nearly impossible as they had gotten mushy and the meat could be pulled apart. We made the best of it and they were delicious, but indeed were marinaded too long.