follower count, subscribers, karma, and reputation.
they were a good measure of credibility from the times of old, times where internet forums were a thing and then some.
but over the years, as you put it, can be bought because a market exist for it.
now all we see are big numbers or a blue checkmark. while they are still an indicator of credibility, it's no longer absolute. We don't know how much of it, if not all are fabricated.
where there is value, there will be forces that will exploit it.
while I don't think this will ever stop, I agree that the transparency web3 brings can help mitigate it.