Easily exploitable without much stretch of a thought.

I'd say closing a program which doesn't work anymore is a better idea.

How so? These bot systems work on volume – there's no regard for how much reviewer time they gobble up. The idea is to make producing reports basically free, so getting 1 in 1000 positives is still a success if you have no regard for externalities.

If they have to pay for reviewer time for each of 1000 reports, then the scheme stops being viable.

The majority of the exploits I can think of are fixed by setting the correct price. Other suggestions in this thread of denominating in bitcoin fix the other exploitation: chargebacks.

If you can think of something that isn't solved by one of those two mechanisms, I'd be interested in hearing them enumerated.