Small Scale Flying.
Last month, I flew down to Portland from out of King County Airport (aka Boeing Field). There was no security check; no security line, no metal detectors, none of that "pull out the laptop" and "take off the shoes" business. The airline desk attendant simply asked me if I had anything flammable or hazardous in my suitcase and she checked it. At boarding time, we walked out of the waiting room across the tarmac, and right onto the plane. I could have gotten from the parking lot to the airplane in 10 minutes.
I'm not sure what key difference to between flying out of BFI precludes the necessity of a full on security check. Someone suggested the theory that "it's a private plane"; but I fail to see how Jet Blue is somehow public. My best thought was that it had to do with the relatively low risk presented by such a small plane. It only carried 9 passengers and two pilots, very little fuel, and it can't fly very far anyway.
In any case, whether or not I think that a minimal security check is a problem depends on how safe I feel when flying traditionally. Though the security at a normal airport has a long way to go, I don't feel particularly unsafe. When I weigh the actual odds of being in a plane crash (one which would have been avoided through security measures, mind you) against the real hours I have saved by flying without security, I would jump at the opportunity to fly Seaport again.