Let's get real, especially these 3 scrapers help the forum a lot, filling the gaps with features we don't have.. for example because the forum software is old.
I don't disagree with you about these three users. There is another one or better to say two more we can add. Ddmr and tranthidung as far as I know. But in these process we are trusting these people. People changes, they will change too. Any bad intend could create trouble for others. In the mean time you have no choice too.
Yes, I've noticed soon enough that I've missed at least DdmrDdmr, but for the sake of example I was fine, hence I didn't edit the post.
I also wrote there about whitelisting. Whitelisting can go in both directions (can be disabled or even become blacklisting). When somebody (who got whitelisting for his scraper) is no longer trusted (and we know how easy is for that to happen) his whitelisting will no longer be granted.
PS. Of course, API keys would be more professional, but I don't dare to even dream about that.