[cracauer]

ITA's customers before the Google acquisition were not interested in sharing large infrastructure that would make contiguous querying (as opposed to on demand when a consumer searches), presumably mostly for cost reasons.

The QPX search engine is actually the same behind Google flights and all the airlines and what Orbitz used to use. The limitation pre google/flights was the on-demand querying only.

Now the contiguous querying, obviously, gives you a load of useful historical data. After running it for a couple of years now they seem to feel confident that they can predict prices changes with enough accuracy that the payouts for misses will be an acceptable price for the publicity, or increased use of their other travel products.

(disclaimer: ex-ITA/Xoogler, opinions my own)