Coast Guard Urges ID'ing of Non Motorized boats
I don't do the sea kayak thing very often so I never really gave this much thought.
Unlike motorized vessels, there is no requirement for kayaks, canoes, and rowboats to be registered, and each year the Coast Guard and state agencies spend thousands of dollars, man hours, and resources conducting searches involving non-motorized vessels found adrift because they were not properly tied down, or were abandoned.
Adrift, unmanned paddle craft such as canoes and kayaks, are considered a sign of distress and rescue crews are launched to search for a potential missing person.
More info available via the US Coast Guard release