The acquisition makes a lot of sense and puts further pressure on the ailing travel publishing market. With the proliferation of smartphones, the market for printed travel guides will continue to erode. Meanwhile, reviews on sites like TripAdvisor have become more important than books for many travelers.
Google's interest in Frommer's is said to be focused on bolstering its local reviews, in conjunction with last year's acquisition of Zagat. But that seems only the beginning. More user reviews should be a boon for Google + Local and has obvious ties into Google's flight listings data which it got via last year's acquisition of ITA Software.
According to the WSJ, "Google hasn't yet decided whether the Frommer's guidebooks will continue to be published in print or whether they will eventually migrate entirely to online". What will be more interesting to me is how Google brings this content to the mobile platform, where it ultimately belongs.