#1 We do our best to mitigate this. Unfortunately, it's also the nature of the business. Availability is constantly changing. It's not just changing inventory

#1 We do our best to mitigate this. Unfortunately, it's also the nature of the business. Availability is constantly changing. It's not just changing inventory though, I've had the same experience repeatedly over multiple days. hipmunk quoted me an itinerary, sent me through to (I think) US Airways to purchase it, and US Airways said it was no longer available and here's the same thing for $200 more. Gave up, tried again a few days later, hipmunk is still quoting the same fare. Only happened for that one fare that one time, though. And I do love hipmunk and use it regularly. (Far more for speculating about places I'm thinking of going than for actually making bookings, I'm afraid).