Many have turned out to be a scam, or at least an underperformed project in the aftermaths (not that the projects themselves more often than not were not pointing in that direction to begin with, at least from the existential point of view).
My first campaign was amongst those that turned out to be a fiasco (exit ICO scam), and even though it looked to me like it had some meaning as a project at the time, you can’t get it necessarily right even if you try to be careful.

Now if one willingly decides to promote a scam because of the payment, that’s not going to reflect good on them, and may taint your account from the Trust point of view. As I said, most of the scam cases are met in the aftermaths, and are generally not known to be so during the campaign itself, but if it becomes a well-known fact, promoting the scam is a no go.