My main problem with Tripadvisor is that it does not really take a hotel's class into account as a variable in its ranking system. As a result, a cheap and clean 1-star hotel might place quite highly on the overall hotel ranking list because of its good value-for-money quotient. I suppose that this might mislead casual perusers into thinking that it is competitive hotel X or Y (luxury properties), which bookend the cheap property in the rankings.

As an example, I used Tripadvisor extensively for a recent European trip. I booked the "Hotel de l'Avre" in Paris on the basis of price and the very positive reviews on that site -- I believe that it's in the top 25-ranked properties in Paris. Well, the hotel is very quaint, but certainly not competitive with luxury or resort hotels, and I therefore couldn't believe that it ranked so highly on the overall list. Tripadvisor should really have three separate lists ("luxury", "moderate", and "cheap") for its hotel rankings, IMO.