Much has been written about Writely and Google Spreadsheets. The consensus seems to be these products are an assault on Microsoft Office. Personally, I see these both of the products as a better user interface for Wikis. Anyone  who has used a wiki understands the power of collaboration that it provides. The difficult part is allowing the average user to create wiki content. What better way to do this then provide an interface that mimics Word and Excel? The real question is not what replaces Office but rather who figures out how to make the Wiki concept go mainstream?