The Marine Corps does not believe in "Special Forces" their view is that all Marines are special forces. They've have fought tooth and nail NOT to be made a part of SOCOM for years ~ but due to the recent terrorist threat of recent years ~ have finally relented.
Therefore they're forming a new "regiment" comprised of RECON and Force Recon ~ (not the same animal ~ there's a difference between the two)
As I understand it, they're not going to be so much a part of SOCOM, as another tool in the shed that SOCOM can call upon, when and as needed.
Most of the confussion about the SEALS, Green Beret, DELTA Force, RECON, Force RECON, and Rangers is in-house poltical among the varioius branches of the military. On the one side ~ each branch of the military has their own ax to grind ~ and dog in the fight. Marine Recon and Force Recon was NEVER meant to to compete with the Green Berets, SEALS, nor Rangers. They were formed to provide reconnisence to a Marine battalion and/or division in the field.
They're Billy Bad Azzes in that they do perform alot of the same or similar type missions that SEALS, Green Berets, Rangers do, but they do what they do to be the eyes and ears out front to let the Marine Commander know what out there and what he's up against.
SOCOM is an effort to bring all these different forces together and to utilize them in their most efficient manner for the task at hand.