One star and five star reviews should theoretically not exist. Therefore any review with these "perfect" ratings can usually be regarded as false. Meaning not written critically, as any decent review should be. Most often, they take the form of,
OMG best book/app/game eva
OR
OMG worst book/app/game eva
These reviews, while contributing to the culture in some weird way do not instill any sense of the items worth into my thoughts, and thus can for all intents and purposes, be deleted from the review system with no real harm done.
Having said that, all reviews are bought and paid for in one way or another. Accept this and move on.