Challenges Implementing Six Sigma

Hi there,

I'm relatively new to Six Sigma. I'm interested in learning about the types of challenges you run into applying the methodology in organizations. Lean, for example, usually seems to fail without top-down buyi-in, support, and representation. That is easier said than done. Some professionals address this effectively from the beginning. Others more concerned with the technical applications and not really aware if implementation challenges usually fare poorly.

Any information on the challenges faced in Six Sigma and how they are addressed would be welcome.