I don't know what authors obsessed over before Amazon.com and their customer review feature, I'm only imagining they led much more complete, fulfilled lives. I learned long ago to stop reading the things, because it turns out the last thing you really want to know is what everyone with internet access and a basic ability to spell thinks of your book. You may trust me on this. For my first novel, a friend left a positive customer review and another reviewer held up something he said as ridiculous because the book was so very bad. My friend chose to be offended, and I rather thought that this wasn't about him.
But, as much as you really don't want to read the customer reviews, you also really, really don't want to use the review feature to castigate your rivals. Because it turns out that people pay attention, and that's when things get embarrassing: