The headline says it all, but I'll say more of course.
After many months of rumor and speculation, Micrsoft is now offering an "all-in-one" subscription service of a web-based version of Office and other applications. It's in private beta for now (by invitation only) and code-named Albany for those of you who want to go back and track the trail of rumors over the past year.
As poorly received as Windows Vista has been since its release in January of 2007, the new vesion of Office that came out the same month has been as widely received.
A web-based version is needed and inevitable, I think. I see the greatest potential for Excel, for example. Excel is a database application and one single document can store literally hundreds of thousands of cells. That's a lot of data floating around as an attachment. It will make sense for a lot of businesses to house their key Excel spreadsheets in one centralized location where it can be babysat and viewed/edited with restrictions.
Ditto for PowerPoint.