Google tightens control over fake reviews on Google Play
A lot of developers promote their apps via illegitimate methods, and fake or paid reviews and ratings are among the most popular. These reviews are a violation of the Google Play Developer Policy, however, since they deceive the regular user into thinking the app is safe, when it actually isn't.
Google further elaborated that developers might want to check with their respective promotion agencies, just to make sure the promotions ran for their apps are legit and don't employ such shady methods.
We here at PhoneArena hope that Google's efforts have a long-term success in clearing the app ecosystem from spam and fraud. In the meantime, we suggest you read our in-depth article on how dangerous apps work, so you can stay safe out there.