Online reviews are perhaps the single most important thing when it comes to building brand trust online. The more positive reviews the better.
There are some businesses that have scammed their way to getting fake reviews, such as the VICE reporter who tricked trip advisor into making him the top ranked restaurant on trip advisor in London. Despite not actually ever even opening for service.
However, despite review scams that may occur, reviews are generally a trusted space where users can get a better understanding of the true experience or service quality.