Reviews are probably one of the most heavily moderated systems on the internet. Not only do you have advanced bot detection algorithms, GEO reviews to IP location, moderators, and trust scores to game, but you have user groups that feel very strongly about the integrity of some of these networks like yelp AND your competition watching you like a hawk. Running a tight ship plus incentivize your existing customers to post reviews is not only the best bet, but the easiest with the best results.