It will be impossible to enforce. The people who don't leave good reviews simply will get dropped from the mailing list. However, it forces the whole thing to kind of move underground, which should help at least reduce the scale of the problem, and creates a deterrent against getting too aggressive with it.
And if enforced aggressively, will only provide a set up for false flag operations to get a competitor banned for fake reviews. I think we've already seen this movie in SEO....
The evidentiary standards for Google search ranking changes is VERY different than the one used for FTC enforcement actions.
I'm pretty sure getting caught for trying to frame a company for buying reviews would bring criminal charges that are more serious than the FTC enforcement action.
