More time is spent in the hotel room than between two people on an airplane anyway, so it makes sense that travelers are willing to pay more for the hotel experience they want.
Kayak already displays some vacation rental listings from sister site Booking.com although HomeAway's properties, many from individual owners, would give Kayak users additional choice. The Kayak-HomeAway partnership could be a nice test for Kayak parent the Priceline Group to see if it wants to cozy up in some form with HomeAway.
Just because the ability to connect with a local in a new city exists, doesn't mean that the local necessarily wants to meet. This theory can be applied to many of the emerging travel tools today.