Interesting perspective on Ding, from news.com:
A Ding-style system allows the airline to not only communicate directly with customers, bypassing the reservations systems, but also to know much more about those passengers--and to predict with greater accuracy whether they are likely to buy a ticket or not. But a custom fare system also allows an airline to identify customers who are willing to pay more for a ticket, and then send them an offer for a more expensive fare. (Ding does not do that yet, but experts say that is where the real money would be.)
"With this new technology, who you are could be more important than when you book," said Steve Hafner, the chief executive of the travel site Kayak.com. "The more the airline knows about you, and about your travel preferences, the better a job it can do pricing its product to maximize its revenues. It is a seismic shift in the way airlines sell tickets."