It's clear when you look at spreadsheets where participants have the same address etc. with no due diligence during enrollment. And of course, considering such users high-risk despite their harm being a spam problem... well, at the end of the day you're effectively calling for more moderation.
The reason they enroll multiple accounts is likely because of some limit, e.g. max posts per week. If I was running a campaign I would call it cheating as it makes me pay more for less and it amuses me greatly to see some seemingly rational and respected users going out of their way to downplay this.
Now what does this have to do with egregious criminals laundering money?