Most travellers are no strangers to Trip Advisor.
I use Trip Advisor to read reviews and get some ideas about properties and destinations, and have posted one review myself. The rest of my efforts are still in procrastination purgatory, sadly :P. Got to do something about that.
Anyway, I read this and this earlier in the week, and my initial reaction was, why would anyone post fake reviews? It's just so unscrupulous and so wrong.
Since Trip Advisor is quite liberal in its posting policy - anonymous reviewers are allowed - whatever opportunity available to boost ratings will be taken advantage of. As reviews are not vetted, property owners and perhaps even its employees can easily post good reviews about their hotel, and bad reviews for competitors. Desperate times call for desperate measures?
Thus the site has responded by putting up a warning label on properties which are suspected to have manipulated reviews.
TripAdvisor has reasonable cause to believe that either this property or individuals associated with the property may have attempted to manipulate our popularity index by interfering with the unbiased nature of our reviews. Please take this into consideration when researching your travel plans.
Elliot's advice is to ignore both extremes; the 'best place on earth', and the 'never again!' reviews. We can still use Trip Advisor, however be wary not to rely 100% on its reviews.
I say, as with some things, take it with a pinch of salt.