I feel as if I've just been tricked into reading a lengthy ad for Twitter here.
http://www.d-n-i.net/fcs/4th_gen_war_gazette.htm is the original article by William Lind that describes 4G War. Bullet point summaries: State (nation) vs decentralized or transnational enemy, psychological war, unequal warfare, everyone's a combatant. Takes a lot from Sun Tzu, really.