Expedia's TripAdvisor (yes.. Expedia owns TripAdvisor...) has gone on a roll up rampage buying 5 content/community players smartertravel.com and bookingbuddy.com; TravelPod.com; Travel-Library.com; and one of my favourite traveller tools SeatGuru.com (according to Hotel Marketing). I think this is a smart move. The model for community/traffic based travel media companies has moved beyond a "one brand fits all model" to a market where consumers are seeking information from a variety of different sources. The synergies are obvious - central ad sales, hosting and management while keeping a low cost production/editorial team. I am assuming here that TripAdvisor will maintain the separate brands and community and not try to do integration crazy (which is soooo 2003).
UPDATE - TripAdvisor/Expedia is not done yet. May 07 announced acquisition of Cruise Critic adding another vertical. Expect more to follow