In the long run, this will probably help Fiverr more than hurt it. I think it will benefit Fiverr to get rid of accounts selling Amazon reviews and they could also do some press release about their steps to stop it. Since sellers are contractors, it won’t hurt Fiverr itself much if any, and they could come out looking like heroes if they play it right (which is fine by me if it benefits honest sellers.)
The other thing is, though, people seeing these articles will hurry to the Fiverr site for other reasons. Some want to see if it’s true you can buy reviews here, some want to buy services that are hard to get cheap and they’ll figure if you can buy reviews, you can get things like testimonials, ghostwriting, honest reviews on people’s blogs, etc.
Most important, people will come here just to “see the crime scene” and will see some gig that looks interesting, go off on a tangent, and become a buyer. They might have missed the Fiverr commercials that show in only limited markets, but they’ll see the news. I recently went looking for a business-related gig that I wanted to buy, and a gig image caught my eye prompting me to order something different from that new seller. I lost track of what I was really looking for, as window shoppers often do.