What puzzles me is that although Locke seems to have replaced Ben, Ben hasn't exactly retired has he? He's still wheeling and dealing, meeting up with Widmore and still seems to have a great deal of power.
Locke may be the leader of the Others but why does Ben still seem to hold many of the cards? Locke kept asking Ben lots of questions but Ben never seems to give him much information. Is Ben holding onto power in another way that we aren't aware of yet? I still felt like Ben was in charge! I just can't see Ben playing second fiddle to anyone!
Perhaps the question shouldn't be "Did Locke fail" but Did Locke ever really lead?