This must be studied, documented and codified -
This is a huge problem that is about to happen or is already happening.
Google will need to come up with some sort of strategy to resolve this issue. We need to put the pressure on somehow.
To date, Google appears to be more about stimulating the process of getting ANY reviews and not allowing for reasonable disputes against REALLY BAD (read illegal, immoral, unethical) reviews.
No one seems to have any real solution to this problem - we have not heard that any lawyers have had any success at removing libelous / illegal or inappropriate reviews.
If you have evidence that Google is actually policing reviews as they should in a timely fashion, please share your stories and best practices here - or link to where they are discussed.