I'm not sure how Yahoo does it but I would think it would depend on how specific the domain name is.
Example:
SanDiegoHotels.com
VisitSanDiego.com
SanDiegoHotels.com is a very specific name in that anyone that would type that name into their browser is specifically looking for hotels in the San Diego area. In this case a 1-click landing page would do.
VisitSanDiego.com on the other hand is a much more broad name that could benefit a 2-click landing page where the first page would have links to hotels, car rentals, restaurants, tours, real estate, etc., which would lead to the 2nd page with the relevant ad links.
Bottom line, domain name specification would be the first indicator.