Bathroom Wall Principle
Jemima Pereira: If you write a poem on a bathroom wall, the owner of the restaurant isn’t obliged to erase it at your whim. Nor should he have to let you back into the bathroom to edit it yourself. He can stick a neon Guinness sign in the bathroom next to your poem. If he happens to hoist his double-wide restaurant onto the back of a trailer and move it to another city (or country), then the bathroom goes with him and he’s still not obliged to do anything about your poem. [via Phil Ringnalda]
One of the amusing things about most legal debates is that one can generally find a number of "precedents" that amount to rough analogies; and each can lead one to very different conclusions.
I personally like conclusions that minimize obligations for all concerned.