I'm glad somebody finally answered the question. It was driving me somewhat crazy, even though I hadn't posted in the thread.
Some guys are just smart base runners. Nobody ever accused Paul O'Neill of being a speed demon and his lifetime % is not fantastic, but in his final season at age 38, he had 22 stolen bases and only 3 caught, and a few seasons earlier he had 15 SB's and only 1 caught.
Of the very prolific base stealers, Tim Raines was the most efficient, with Willie Wilson close behind.