People, let's try to stick with facts, here.
Older Sportsters (and big twins) ran DRUM brakes with sprockets on them. The drum protected the brake surface from grease. Tapered bolts need a certain degree of precision to ensure contact at the tapers. If so many of these hadn't come loose I'd just say well, it's good enough, but since so many have....
When I was at MMI (20 years ago) they told me to clean ALL brake rotors I come into contact with using alcohol based cleaners to avoid contaminants. I, personally, prefer that to "It'll burn off anyway" from the guy who's getting rich selling them, but maybe that's just me?
Nobodies attacking anyone personally for choosing sprotors. If you feel good about your's, then fine. I just feel strongly about this, because I've seen so many guys get sold these things without a hint of truth involved. Then, when they come apart the customer is shocked! No one should be shocked that a sprotor failed. So many have failed that I am surprised when one works for very long at all!
My motivation is to prevent people from locking up their rear wheels and ending up on the median. At least if I speak up, they will know it's possible. If your motivation is to justify your personal investment in a product, or to help sell a product, then I tend to doubt the veracity of your stance.
Yes sprotors can work to some degree. Yes they might last longer given certain riding styles and conditions. No you cannot install them and have as much faith in them as a conventional brake, PERIOD! I've seen conventional set ups fail (actually only pulleys/sprockets, never rotors), but it's almost always incorrect installation. I've installed sprotors with all the care I can muster and found 'em loose a coupla thousand miles later. I warn anyone who want's these things about the known dangers, because it's my job to.