Take this guy, Donald Mitchell, written about on Forbes. He is one of the top five reviewers on Amazon:
"Something about Mitchell's prose inspires people to contact him. He receives a handful of e-mails a day, most often from people who want to learn to read faster or start their own businesses. "A lot of people will contact me about advising their children: how they can get into Harvard, what they should do for their careers." He also hears from women who want to divorce their husbands. "I try to send them information and resources," he says. "They never explain why they pick me out." He tries to respond to everyone.
"Reviewing has its perks. "People are always inviting me to go on trips with them," he says. "If I have reviewed a travel book, they'll invite me to go to that place with them." He gets frequent dinner offers (which he accepts "occasionally"), and after mentioning in a review that he had never played on the Yale golf course, a reader invited him to play there. He accepted.
"Mitchell has parlayed his reviews into a profitable enterprise. For authors who write books that Mitchell wouldn't typically review, he'll ask them to make a $600 donation to Habitat for Humanity. The donation doesn't guarantee a favorable review, although Mitchell concedes that he'll try to make it longer. He originally charged $25 and has since bumped up the price. "I'm probably not charging enough," he says. "A friend told me I should ask for $2,000." Mitchell has donated his $20,000 in review earnings to Habitat."
Read more here.