The Marriott Hunt Valley Inn appears to have an extremely frakked-up wireless network -- it's assigning client addresses in a completely different netblock from the default gateway. This problem appears to be popping up in Linux for some reason, although my Android phone works fine. The solution:

sudo route add -net 172.30.1.0/24 ath0
sudo route add default gw 172.30.1.1

You will now be able to type a random URL into a browser and click through to teh Intarwebs. THIS HAS BEEN THE VOICE OF THE MYSTER-OPS. WE KNOW YOU CAN HEAR US, EARTH FEN.