Anti-missile blimps for Washington DC

This story just strikes me as odd... Are the Washington elites growing increasingly paranoid?

From National Journal:

Within a year, a pair of souped-up $2.7 billion blimps (price includes R&D) will be floated 10,000 feet above the District of Columbia and act as a 340-mile-wide eye in the sky, detecting incoming missiles and the like.  

The design and testing phase for JLENS—the (deep breath) Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System, produced by Raytheon, a major weapons manufacturer—is over, relays Program Director Doug Burgess to Popular Mechanics. Now, it is time for implementation.

How come just DC gets the blimp-based shield? If there's a threat, is the seat of government the only place deemed worthy of this extra layer of enemy detection?

Who can get close enough to lob a cruise missile at the Washington DC that traditional detection wouldn't pick up? It's not like cruise missiles are intercontinental... nor are they easily improvised.

Are we talking cruise missiles launched by submarines (the Russians have been more aggressive in east coast patrols in recent years), or are we talking something launched from a improvised merchant ship platform?

Who are the presumed potential cruise missile attackers? Other nations? Terrorists? Rogue U.S. troops attempting a coup?

If it's the Ruskies' new subs that helped justify these new defenses, is this really the time for a president to prioritize reduction in our nuclear capability?

I'd love to have more data points here. The information presented in the root article leaves me with more questions than answers. But my curiosity has been aroused.