Knight Ridder reports that even the U.S. Coast Guard boat throttles down and moves aside when the Susan M., Alameda County's new 85-ft. homeland security patrol boat, blasts past Jack London Square toward San Francisco Bay. The Coast Guard boat is said to be a key component of the East Bay's defense against a water-side terrorist attack. But the county's twin-engine cutter -- a sleek fiberglass vessel with a menacing pair of .50-caliber machine guns adorning its bow -- provides proof that there's a new player in town when it comes to guarding the Bay Area from offshore intruders. Alameda County, led by its sheriff, Charles Plummer, has…