...But unless you have a lot of personal experience with lost or missing luggage, there's no reason to be afraid to just let your stuff fly under the plane...
I fly internationally at least once a year, and make several trips around the USA every year. I fly with Southwest, Delta, American, Continental, etc.
I would guesstimate that about 1/3 of the time at least one of my bags doesn't arrive at the destination with me. In all cases, the errant bag has arrived at my hotel by 6 a.m. the next day.
Those are extremely poor odds. My regulators, cameras and prescription masks stay with me as carry-on luggage.