Agent reviews are becoming more important and used by many potential clients to help in selecting an agent to work with. The need for these reviews is so important that many may resort to paid sources. You really need to dig deeper and look at reviews that are verified independently. Websites like the Better Business Bureau and Dave Ramsey are a subscription based service with a per per lead on top.
These companies have a great reputation and their endorsement comes at a cost but just because the website endorses a real estate agent doesn't mean they are great at their business.
Can anyone join, maybe! If you are willing to pay. So where should you go for authentic reviews? Websites we all know and use. Zillow and Trulia have been able to maintain the integrity of reviews and are a great source for those reviews and sales history.