To be fair, he didn't specify that the reviews were false. Maybe he only agreed because he legitimately likes the vacuums. I think if someone offered me a product I like for free in return for a review, I'd do it. I wouldn't leave a positive review on a bad product though.

I see where you are coming from, but this is Amazon, a juggernaut which is impossible to render accountable. So, OP is effectively filling their shed space with things which are useless to them and whose monetary value they won't realize. They are also tainting their soul. But by posting fake reviews, they erode trust on Amazon and cause it (some) financial harm. OP is, thus, doing a public service at some personal expense.

I often buy products from Amazon based on how fast they can deliver, with the soonest being approximately five days where I live. They routinely advertise one delivery time and deliver three or four days later, which essentially is false advertising and harmful to local businesses who could easily compete on delivery time. And this is Amazon fulfillment.