I think he forgot option 5: whether Bing intentionally copied Google's search results or not, if Bing continues this practice then their index will contain a de facto copy of Google's index for tricky queries. Bing will inherit Google's spelling correction, it's long tail, its top results, and any other enhancements Google develops to return more relevant results.
Google invests so much into these things; if Bing absorbs these improvements without lifting a finger, Google loses its ability to stay ahead through technical merit and innovation.
I think Amit is telling the truth: "And to those who have asked what we want out of all this, the answer is simple: we'd like for this practice to stop." http://googleblog.blogspot.com/2011/02/microsofts-bing-uses-...