It is merely a (predictable) result of not putting real teeth into sanctions for those who are caught cheating. The system that is currently in use is mere window dressing, it gives off an appearance for those who are convinced by a casual glance and do not care to take a deeper look inside. It does not work well enough to give a real appearance that there is genuine interest in ridding the sport of PED cheats. The athletes play a role and bear some responsibility but to me it is ultimately really up to the administration to act (or not) to do anything and everything possible to ensure that a culture of PED use does not exist and flourish. Yet the administration builds the sport on the backs of the athletes and their image. And as we have seen, they have been acting to enable the PED cheats going back at least as far as 1984. They profit from athletes like Bolt, Marion Jones, and others being in the public eye for their performances. Cycling took a massive PR hit when they decided to start throwing a bunch of riders out of the sport a few years ago. As a result, they exposed their dirty secrets to the world yet subsequently gave the impression that they were indeed serious about cleaning up the sport and keeping it that way. (Incidentally, I still consider pro cycling to be a very dirty sport; pulling a sport up from being saturated in a PED culture like that does not happen over the course of just one or a few seasons. But then my sentiments regarding pro sports are no secret, I am sure.) Other (more popular) pro sports (cough!-NFL-cough!-MLB-cough!) lack the brass to really stand up to PED cheats and make them pay a high price for their actions so unfortunately there is a real disincentive to be the sport, in a market of ever-increasing competition for sets of eyes, that starts busting top stars and throwing the rats out. As much as I might prefer to see that happen, those who control the pursestrings in the sport clearly would not.