Actually, I'd not call it "dumb." Things, not solely trafficking, are detected quite often. While there are undoubtedly bad elements out there who could conceal something and get away with it, most people are not master criminals. People make routine mistakes all the time. As for randomness, it's true that might be more effective. Or, you could look at it from Disney's perspective--which is more than just liability and media related--that if most people know that checks happen daily, it makes illegal acts less likely to occur. Why bother with a resort or group of resorts that is systematic in their room checks when you could easily find one less high profile? Finally, as implied by the author's original post, even now people come to Disney resorts without realizing the checks are daily, so that introduces the surprise, aka randomness, element to some degree.
I'm not a huge fan of the checks from a CM standpoint--they are a pain. As a long time
DVC owner, even before I was a CM, the checks never bothered me. First world problem.