So who owns a review? Product reviews are known to work on travel websites but when a consumer adds a review who owns it?
This isn't completely clear and different solutions have very different answers.
Take for example Visitor Review from Digital Visitor. For their service (£150/$240 a month), Digital Visitor retain the copyright.
They have a medium sized list of travel company clients including the VisitBritain DMO site (See reviews page).
As confirmed by Digital Visitor, if VisitBritain cease to use the Visitor Review system they can't take their reviews with them.
Additionally, any other travel website could come along and, having formed a deal with Digital Visitor, use the VisitBritain reviews.
A second example from a similar service (PowerReviews Express) - their system starts at £50/$80 a month. They are very clear who owns the content.

"You own the content. If you are not satisfied for any reason, you can end your contract and stop the service with 30 days notice. You will still own all review content collected up to that date."
To me this is critically important. If you own the product you need to own the copyright to reviews of those products if those reviews are on your own website.
If you don't care too much about who owns the copyright then you may as well use a plugin from TripAdvisor. TripAdvisor owns the copyright to all reviews on their system but additionally give you significant marketing exposure. If you are going to give your copyright away you may as well make your content work for you.
Final thought - should the consumer own an aspect of the copyright to their own reviews? It is their review after all?
For example on Ning-powered communities (I run two of them) if a user no longer wishes to be part of the community they can leave and have an option to delete their content. Quite annoying for the community owners but absolutely fair to the community members.
The copyright question will matter over time - right now people are forming contracts with review system providers. Doesn't seem much consideration is being given to what happens at the end of these contracts.