Cuil. On a serious note, it seems to me that barrier to entry for search is now exponentially higher than it was when they started. I'm not sure if it's even doable with small resources (in proverbial garage) anymore.
I keep mentioning "restaurants near me" in this thread because it's absolutely killer that's possible now.
They could also provide the pure search index for other companies by using their cloud infra, and charge for the cloud use instead where Bing would be only one of the clients of this open search index.
It was basically the strategy the open source world with the lead of Linux did to them, and were able to take down their dominant monopolistic position over software.