If there’s way to keep our computers clean, stable, less power consumption and it’s free, open, portable, widely used, why not go for it? For videos, why we have to spend time and energy to convert our MP4 to FLV? For document sharing, if it can be done well with only the browsers, then why we need to open PDF reader? Even we can replace word processing, spreadsheet by we services. Scribd is showing us a great demonstration here in HTML5.