I've noticed that guests sometimes get confused about where they actually stayed and then write a review for the wrong property...
In Asia if a hotel gets in LP and has good reviews, you often find other hotels changing their name to the same or at least something similar.
After thinking about starting my own guesthouse I have started reading reviews of hotels on TA that I know of in my area to get more of an idea of what is out there.
Most reviews of places seem to be fairly honest but others have very petty complaints. Some things that people complain about are beyond the control of owners anyway.
I think there needs to be some way that people who left reviews actually stayed at the hotel/hostel. TA and other review websites probably need to have a "trusted reviewer" membership level, where the member proves their identity in some way and develops a history of providing fair and accurate reviews.