I have heard this subject brought up a few times here on BF. I suffered from toe numbness and with the help of a professional I have overcome the issue. I am posting this to help others who have the same issue. My toe numbness came regardless of how tight my shoes were. It always came around the 12-18th mile.

1) Orthopedic shoe inserts for flat feet. I do not really have flat feet, but the way that the shoes fit do not conform to my arch well. I got custom inserts made, however I was told that buying generic heel insoles would work nearly as well.
2) Shoe tightening: Contradicting my original school of thought, try keeping the toe straps slightly more snug than the upper strap and the ratchet strap. No straps need to be any tighter than what is absolutely required to keep your shoe from moving around.