We're not sure what type of listing we would have expected to be the most popular on Airbnb, so we can't necessarily claim to be surprised that it's a tiny "mushroom dome" cabin in the woods of Monterey Bay, California. The adorable little abode rents for $115 per night, but of course, being the most popular, it's basically impossible to get a reservation unless you're willing to commit very far in advance.
• Mushroom Dome Cabin: #1 on airbnb [Airbnb, via Inhabitat]