How did Osama escape?

I always offer a caveat when linking to Daniel Hopsicker's work, but this piece is worth reading nonetheless. Did we lose Osama Bin Laden at Tora Bora because the job was "outsourced," as Kerry has claimed? General Tommy Franks says no. Hopsicker offers an interesting counter to Franks' argument. Just how did the world's most wanted man manage to walk away from an assault by the world's most powerful military?