Another point about sites with lots of link equity - many times big organizations have too complex a business structure. They aren't agile enough to get millions of URLs into the index without all kinds of dupe content, server complications, internal cannibalization - on and on.
Overstock.com is to be commended for achieving 10 million indexed URLs. That's no small feat. I know of some major brands that need two years to get management approval just to fix an issue that any affiliate marketer could handle in 5 minutes. This may be because Overstock is a pure web play, unhampered by a parallel business in the physical world. But it still takes a lot to achieve, even so.
I was not following the internal development of the website before this thread, so I don't know if Overstock made any infrastructure changes last year, or reorganized their information arhcitecture, link structure, URL formats, canonical fixes,etc, etc. But those kinds of factors are often the essentials for a big brand to compete on non-branded keywords.