Google's Bing-sting to "prove" that they were copying search results is noteworthy for how elaborate the operation was to catch the hand in the cookie jar. What does Google have to fear from Bing? Here are some reasons that Google might be feeling vulnerable right now.
Google Does Not Own The Web Index
All search engine indexes are essentially public domain because all of the content in them is in the public domain. No one pays to be in the organic results and no one explicitly gives permission to be indexed - although everyone has the ability to opt out of being listed.
Furthermore, whilst Google may be said to possess it's own unique methodology for ranking websites, in reality there is very little way of proving one search engine is using any particular methodology over another. It's a matter of irony that no one can really prove that PageRank is even being used on Google, aside from the toolbar PR rating which is broadly understood to be inaccurate and of no longer of any use to webmasters.
One of the problems of having less competition in the search space than previously enjoyed is that it means that Google has become the defacto standard of search quality. There are few other options that are sufficiently different to make one search engine seem significantly better than another.
Thus Bing has nothing to lose by copying Google results and everything to gain by using Google's own data to replicate results. If that's what the people want, maybe Bing should just give it to them - after all, if search engines do not own the destination content of the web index, then they can't really be said to own the search results either.
Put another way, I can hire a cleaner to clean my house, but my cleaner does not own the cleanliness of my house - only the quality and efficiency of their work. Whether I choose Bing or Google to clean the web for me is pretty much irrelevant - as long as i think the end result is to the quality i expect. This has always been Google's achilles heel despite their search dominance.
Google Uses Toolbar Data To Organize The Web
If Bing is able to create a mirror of Google results purely based on competitive toolbar data then it would suggest that toolbar data is pretty important to how Google ranks websites. This flies in the face of Google's much vaunted and ever changing '200 ranking factors'.
Whether Google set a honeypot or not to catch Bing is again irrelevant if the latter can provide it's own users a best guess as to what it thinks they want. It stands to reason that the best guess as to what users want is anything but a 'zero results' page if Google is serving results for those pages. Why not just copy the results? If the same toolbar data is flowing through the Microsoft browser as it is through Google's, why not make use of it as a matter of competitive intelligence? And if Bing can do this, then why can't Apple?
Google's Own Search Index Was Built From The Yahoo Directory
When Google first started out, one of the major backbones to it's organization of the web through PageRank was by indexing the original, human editted, Yahoo Directory. In essence that was the guarantee of quality sources from which the machinations of PageRank flowed. It is also worth noting that Google's AdWords pay-per-click engine which is responsible for nearly all of the search giant's revenue violated a patent owned by Yahoo - a dispute which was settled in 2004 when Google bought a perpetual license to use it.
Google Does Not Exclusively Own The PageRank Patent
The original founding principle behind Google's secret sauce is the PageRank algorithm, will become a non-exclusive patent this year.