Since I usually enjoy your comments on the California Power Crisis, I am reluctant to point out that the ferry system is something regulated under federal law as a "common carrier." There are lots of requirements on "common carriers" having to do with access to all, no favoritism, and rules to make sure that commerce is fairly served. Based on my limited business law knowledge, there is a huge difference between a "common carrier" and a typical private company.
I'm sure that if I pulled up with a leaking Propane Delivery Truck, they would not allow me drive it on and park it on one of those ferries if they knew that I had a slow propane leak.
I hope that random searches are used. If one does not want a random search, they don't have to ride the ferry. Same thing applies in our airports. You have a problem with a search, then don't fly!