Basically, until we have a concrete proof (such as Armstrong in cycling), it is extremely cynical to assume that the same is true in tennis at the very top of the game.
Lance Armstrong was never tested positive despite hundreds of tests.
No east german swimmer was tested positive during the 70s 80s.
No chinese swimmer was tested positive during the 92 olympics and 94 worlds.
Marion Jones was never tested positive.
So people who assumed they were on drugs were extremely cynical?
Not to mention that Armstong, chinese swimmers, jones, etc got OOC tested FAR MORE OFTEN than current top tennis players. So we are not allowed to be cynical just because drug testing in tennis is very lax?