That really only works for high-demand, current products. Back when I used to be engaged with Amazom I wrote a lot of reviews for out-of-print secondhand books

That really only works for high-demand, current products. Back when I used to be engaged with Amazom I wrote a lot of reviews for out-of-print secondhand books that I borrowed from libraries or bought from specialist shops. I was usually quite harsh with my reviews but was often the only reviewer and usually the book was out of stock at the time. People seemed to appreciate the long-tail reviews and I was up in the top 100 UK 'most helpful' reviewer list. If I had only reviewed books I'd bought on Amazon I would have written about 10% as many reviews.