For a long while it seemed that while ebooks could be a profitable option for writers, particularly when they were writing about niche subjects, the medium was still struggling to crack a really large audience and become "mainstream". But it looks like that barrier has been broken now. For the first time ebooks have out-sold traditional books at Amazon, with Kindles being purchased in huge numbers.
Of course this doesn't necessarily mean that the same thing will happen across all book retailing sites. However, it is highly significant. And I suspect it won't be long before the sight of people using e-readers will be as common as the sight of those listening to their beloved iPods.