I've got to admit, I probably never do any stretches or warming up before a hike. But, one could also make the argument that for many of the activities I do, the hike itself is usually serving as a warm up or sorts. I hike a pretty good jaunt before I climb the rocks on the coast. I hike a good jaunt on the flat lands before I even get to the hilly parts. As for kayaking, taking those jokers off the roof of the car and getting everything ready for the water is a warm-up in itself.
But before a hike? Usually, I don't do any warming up.