As a kid, I remember Marines not being too fond of the idea of a Marine "Special Forces" unit, but 9-11 seems to have bolstered for need for asymmetric warriors across all branches, including Marines.
http://kitup.military.com/2011/06/marsoc-could-grow-to-seal-strength.html
MARSOC Could Grow to SEAL Strength
http://kitup.military.com/2011/06/marsoc-could-grow-to-seal-strength.html
MARSOC Could Grow to SEAL Strength