When a site has too many positive reviews, than you know they are fake or were paid to give their opinion. You see something similar on Amazon; some people get paid to review some items and in 95% of the cases, all these reviews are positive to very positive.
Not really fake, there are casinos and other companies that want to know the feedback of their user so they somehow put a pop-up on the site and ask their user to give a review. Other people who are not into giving feed back are then, due to contentment to the site, then give their positive feedback. So if we see lots of positive review on the site we can check the format of the review if it is a fake or not because review made by shills are almost identical.
Before it was pretty obvious when all the reviews were posted by shills, nowadays it is not so obvious anymore. And a lot of sites, ask for your feedback, for how many sites do you really do it? Most people (including me) just click than away when you are having an OK/good experience. When something is bad, you will probably already be more inclined to fill it in.