TripAdvisor isn't exactly a wild-eyed daredevil, but the fastest growing category on its Flipkey accommodation site is apartment rentals, a category that flirts with illegality in large, urban markets ...

TripAdvisor/FlipKey's challenges with the vacation rental industry aren't only technical ones. They also reflect increased supply available from individual homeowners and apartment renters.

Last fall, my wife and I used TripAdvisor to find a rental condo for a trip to Manila. We chose one that looked excellent in the photos and were directed to FlipKey, which books TripAdvisor’s vacation ...