The ASA (Advertising Standards Authority) is investigating Trip Advisor. This is a well-known UK website which features comments on the quality of hotels and places to stay.
Comments in question are both negative and almost malicious, while others are too fulsome in their praise to be from impartial consumers.
The ASA has only had responsibility for websites since April 2011. Whatever the result it is a strong message to website owners to check the validity of their sites.
Comments on most small business websites are likely to be testimonials. Of course these should always be authentic, but now there is a legal watchdog some businesses might do well to adhere to best practice and make sure they are verified.