According to this article here Microsoft is actually spying on Google’s search results (via the Internet Explorer browser or possibly some of its plugins) to enhance its own.
The article is pretty extensive and the evidence appears damning. Bing doesn’t deny Google’s claim. Indeed, the statement that Stefan Weitz, director of Microsoft’s Bing search engine, seems to confirm the allegation:
As you might imagine, we use multiple signals and approaches when we think about ranking, but like the rest of the players in this industry, we’re not going to go deep and detailed in how we do it. Clearly, the overarching goal is to do a better job determining the intent of the search, so we can guess at the best and most relevant answer to a given query.
Opt-in programs like the [Bing] toolbar help us with clickstream data, one of many input signals we and other search engines use to help rank sites. This “Google experiment” seems like a hack to confuse and manipulate some of these signals.
So perhaps Bing is not actually copying Google specifically, only watching what people click on in all search engines. Clearly this is open to massive abuse by SEO experts and it won’t take them long to manipulate Bing’s results in their favour! Its search results will actually suffer as a result.