Drifting happens. However on properly made trails you shouldn't have to brake in the corner and nail it with tonnes of speed...
I think one thing some people are mixing up is the differences. Skidding is annoying and almost pointless, drifting is a very useful method for turning the bikes in the proper situations (at least thats how I was taught). Drifting you don't use the brakes and end up countersteering. Skidding is for kids who haven't learned body position turning. Most dhillers (generally signifigantly faster than most freeriders) don't use their brakes much and I doubt ANY of them would ever recommend using your brake mid corner. When you engage your brakes on a full suspension you lock or partially lock your suspension in place. This removes the ability of the bike to assist in the turn by adding traction and in a sense you end up riding a ht through the corner, thats pointless. You brake before enterring the turn and then explode out of the apex. 180 degree, switchbacks, berms...the theory is the same. In all honesty if you are braking in the turn you need more practice on the bike, because you are braking at the wrong time anyways.
Both drifting and skidding cause more damage than just pedalling through, I tend to only drift when I am on a maintained mountain/trail. I have the bonus of living in an area with a paid for mountain and a very very active trail crew.