Don Dodge, in saying Microsoft Will not Fall into the Innovators Dilemma, compares Google Apps for Your Domain to Office Live, but he misses Christensen's point on how successful businesses gets stuck making only incremental innovations.
The real technology disruption here is that Google Apps for Your Domain (and Google Docs, the free version) use HTML as their native format, not Microsoft's crufty legacy format, nor the equally crufty XML data-dump. Writers who use Word every day, like David Weinberger and Teresa Nielsen-Hayden, get stuck trying to make it behave and judging by the comments on both those posts they aren't alone. When my friend Maf was working on Microsoft Office, he summed it up by saying "every time I tell someone I work on Word they tell me it's far too complicated, then ask for 3 more features".
Most people use Word because it is the default - they have to use it because others do too. They do not use its advanced features, they just type stuff in. Fifteen years ago, I was a keen Word user, and spent hours working out how to do well-laid out tables in it, and carefully constructing style sheets so that they behaved right. Nowadays I do those kinds of things with HTML and CSS, which are open technologies that anyone can implement and use.
HTML is now the default document format, and an easy wysiwyg editor for it is long overdue. GMail's automatic conversion of attachments to a hosted document with version control is just the kind of 'worse is better' disruption Christensen documented so well 10 years ago.
Oh, and by the way Don, Nintendo Wii is the disruptive innovator in consoles too.