Which, to my (probably outdated) knowledge, is why they used Silverlight for print preview. The key here though is that I can log in to any random machine with

Which, to my (probably outdated) knowledge, is why they used Silverlight for print preview. The key here though is that I can log in to any random machine with any common browser and use the primary features of Office. Google Docs offers me the ability to read a spreadsheet on a kiosk in a hotel, so Office web better do it too. If Silverlight was required, that wouldn't be realistic until it achieves Flash-level or greater adoption.