The problem is, what happens when someone buys 100 reviews? If there was marketplace curation - wouldn't matter, still only 4 listings for SD card 16gb. But with 600 people competing and buying reviews for SD cards? Who knows what shows up as the highest reviews...
FWIW Amazon has 1,826 results for that query, and Jet has 35. I am sure Amazon has more unique products, but not that many more.