Register your moped. In Michigan, it's not such a hassle. But you should definitely do it. It's great for when you find dirty little thieves and arrest them until the cops show up (standard ops for the Army during "moped season"). Having a title makes sure the cops don't give you hassle.
It (registration) also helps a bit in recovery. So do register your peds. A nice trick (if the fees are high) is to make a fake bill of sale (standard ops here) for $10, since most fees are based on a percentage of the bike cost. Just a tip.