Yep, sprinting is the prime example. If an honest but genetically lucky and hard working sprinter came along today, there would be no way they could convince everyone that they were clean. Not getting caught doping is assumed to mean you are just too good at hiding it.

The dopers have basically ruined sprinting and a number of other sports for anyone who wanta to compete cleanly and does well.

It's entirely possible that Bolt is clean and is a Phelps like genetic outlier, but there will always be suspicions that can never be disproved, no matter what he does.