Yesterday I saw a documentary where some showed software that predicts developments in airfares. Similar to weather and traffic predictions a user would get a prediction of price developments when airfares for a specific connection are searched. Based on these prediction you could make an educated guess if you need to buy now, or better wait some time.
Since watching that documentary I have been searching for a booking site that uses this prediction feature. In the documentary they mention that such a webservice is not yet available in Europe, but since the Internet is more then Europe only, I expect to find a working example. No luck so far.
The documentary was a Dutch documentary, where they explored the actual costs of flying an airplane from Amsterdam to London. The objective was to find a reason for the fluctuating real airfares asked.