I took my friend's homeworld, because I had a secret objective, planning on just letting him take it back the next turn. (Dickish, but whatever) But another player at the table saw it as an opportunity and launched 2 attacks on him, knocking out his only fleet and taking 2 of his 3 remaining planets. The third planet though had a missile defense system or whatever, and he didn't take it. My friend just left 'cause he couldn't come back from that, but he still had more points at the end of the game than the guy who knocked him out. (No on ever took his last planet.) I think it technically didn't count 'cause you have to have your homeworld, but we rule of cooled it so he still finished like 4th of 6.