Cool! I like the suggested line: "I like my tummy rubbed".
You could program all kinds of important stuff like favorite beer, how you like your steak prepared, etc.
You could also use it like a mini PDA to store phone numbers for your favorite LBS, cab company, etc.
Realistically though, other than your name, address, and emergency contact number, and drug allergies, there's really no other information needed on a cycling 'dog tag'. If the tag becomes neccessary, it's because you are in bad shape and things like insurance information are not needed to get critical care.
Still, the dog-e-tag looks like a great conversation piece!