I think we're mostly disagreeing on the meaning of sketchy, but it has many meanings. I'm using it to mean "legally dubious, in the sense of being full of scams, blatantly false promises, malware, etc." (I'm also ignoring issues around copied/pirated content). I'm sure Twitter contains some of the above, but they try to minimize/eliminate it.
But I think this is all a distraction from what I was trying to convey -- my point doesn't depend on getting to the bottom of what is meant by "sketchy". Just define X to be some kind of website that has extremely low value advertisers (scammers, etc.):
> [X] websites do have advertisers, just extremely low value ones. Twitter wants to maintain a pleasant environment for the medium to high value advertisers, [...]
