I agree that it is dangerous and that is why it has to be judged carefully, but it is clearly still evidence that must be taken into consideration. Any benefits given to the witnesses must also be taken into consideration when judging the reliability of their evidence.
Courts of law all over the world rely very strongly on witness testimony so why cannot the USADA?
If people are clever enough to hide all physical evidence of guilt does that mean they cannot be convicted even if several people saw them commit the crime?
I don't know the answer as to whether he was clean, or not - what I would say, though, is that if the rules and regulations of the cycling organisation he was competing in, require positive tests (be they urine, blood, or both) then without that damning him, I fail to see that he's got a case to answer in terms of the sporting events he competed in, and any titles he won, if there's no biological testing that withstands independent scrutiny, that can definitely be proved to be his, and not interfered with.
As somebody largely ambivalent, with maybe a passing admiration in terms of him beating cancer, then returning to cycling and winning, I've not been following it too much or too closely. But from where I'm sat, it does seem something of a witch-hunt, and my understanding of the people testifying, does seem somewhat compromised in terms of their impartiality and credibility.
Courts of law, criminal and civil cases dealing with testimony are one thing - but this is rather more specialist than that - if all you have is hearsay - whether from more than one person, or not, for at least some of them, they're damaged goods.
The other thing, too, is that some are inclined to support this because they dislike him - which, again, seems rather biased, really.
I get the no smoke without fire thing - and I also get that he seems to be a target of some of his own making. All the same, I can't help but feel there's something disproportionate about it.