Perhaps as a hedge against Google's acquisition of Zagat, Kayak went ahead and added professional hotel reviews from Frommer's and Budget Travel.
So if you do a hotel search for hotels in Boston on Kayak.com, you can now filter the results to view professional reviews from Budget Travel and/or Frommer's, and can still access user reviews which Kayak aggregates from around the Web.
Kayak displays a snippet of the Budget Travel and Frommer's professional reviews, and then users can navigate to the respective websites to read the full reviews.
So Kayak now provides a well-rounded review assortment of reviews, including those written by ordinary travelers and professionals.
The filters make it easier for travelers to narrow the scope of their searches if they want to opt for professional reviews.
The partnership with Frommer's is not a one-way street for Kayak: the agreement calls for Frommers.com, in turn, to integrate Kayak travel search and content, as well.
Google acquired Zagat several weeks ago so it could offer its user reviews about restaurants in Google Places and elsewhere after dust-ups with Yelp and TripAdvisor over Google's use of their content.
Kayak hasn't acquired Frommer's or Budget Travel, but has now made arrangements to secure their content and integrate it through the use of search filters on Kayak.com.
Disclosure: The author freelances for Frommers.com.