CIA goes military?

I remember reading about the CIA and assorted military or quasi-military events back in the day (LOL, ain’t I hip?) or at least back in the ’50s and ’60s, before they got busted in the wake of Watergate. I don’t ever remember reading, though, that the Company had formed an actual military unit. Now, apparently, that has changed and this unit, the Special Activities Staff, is leading the way in closing in on bin Laden. Not really sure how I feel about the news of this group though. I wonder why the CIA needs this capability, instead of just working with an appropriately trained, staffed, and equipped company from the Marines or the Army.