If your business is getting negative reviews from competitors pretending to be real people, then you can always flag and report that review to Google. Google is good at figuring out if accounts were created for purposes of posting reviews only. Some people actually create fake Google accounts or ask people that have never been to the business itself to post a positive review on Google places.
An SEO dude emailed me asking me to kindly post a positive review about a place that I have never done with. I simply ignored him.
Sometimes a legitimate good business can receive a bad review by accident when a person clicks a business with a similar sounding name. If you believe that a negative review was posted by accident and that you did not do any business with the person who left that review, then consider contacting Google to have that review removed.
Visit the Google official page for this matter.