Now, that's being populated further with TripAdvisor ratings. The feature is available now on the U.S. and U.K. Kayak sites.
The addition of TripAdvisor gives Kayak the potential to further reach out to a younger and more social media-friendly crowd.
TripAdvisor functions much like Yelp or any other reviews site, but usually with a specific focus on hotels and hostels worldwide. Many of the 60 million and counting reviews for destinations worldwide are quite honest (sometimes brutally so), and they include user-submitted photos.
Both Frommer's and Budget Travel are also veritable sources of travel information, and they tend to offer more for family-friendly crowds.
Although the extra source of information will likely contribute to more traffic on Kayak, the travel search engine seems to be doing pretty well already.