Makes sense to me. Apple doesn’t want to build search engine, but could control search experience via Bing.
One other theory not mentioned here but on Twitter from David Weiss is that Apple would want more than just search and money. My thoughts went to the claims that Apple was concerned that it’s Multi-Touch patents were weak. Perhaps they are, but for how long Microsoft has been researching and experimenting, I’m sure they have some strong Multi-Touch patents.
Perhaps Bing + an agreement to not sue each other over Multi-Touch and maybe encouraging Msft to enforce some of their better Multi-Touch patents?
Regardless of why, I personally would love an Apple UX over Bing. I’ve been very pleased with Bing search results. And I love my iPhone. Match made in heaven?