No matter what Is it? The fact is that "Google is allowing a single domain from a well-known brand to dominate the first page of search results on some brand-related searches." In the screenshot below, the first seven of 10 organic/natural results are from apple.com. There're some shopping and news results mixed in, and other sites have the 8-10 spots. But to rank a single domain in so many results on a single page is unprecedented. The same thing appears to be happening on other brand-related searches."
Just couple of weeks ago, Google's Peter Norvig specifically talked about the need for variety in search results.
We've asked Google for a statement about these brand-dominated search results, but they didn't replied at this point. In the meantime, Bill Slawski's post refers to a Google patent about "How a Search Engine Might Assume a Query Implies a Site Search."