Note that there were recent layoffs at [link|http://www.news.com/AOL-lays-off-750-employees/2100-1024_3-5482478.html|another big player out there]. Traffic on the [link|http://en.wikipedia.org/wiki/Dulles_Technology_Corridor|Dulles Corridor] can be a problem, and a couple of the major arteries are [link|http://www.dullesgreenway.com/cgi-bin/dgmap.cfm|toll roads].
Make sure you understand the +/- of the area if you're thinking seriously about northern VA. Housing can be very spendy, and traffic is a continuing problem (though it should be a little better when the new [link|http://www.wilsonbridge.com/|Wilson Bridge] and the [link|http://www.springfieldinterchange.com/|Mixing Bowl] are finally done).
Good luck!
Cheers,
Scott.