Although solving a critical problems is a significant advantage (especially in the b2b market), I think it is also possible to establish a business based on adding-value or improving upon various aspects of a business or consumer experience. Add-ons to existing products and web apps that simplify a more complicated workflow are good examples.<p>I find that much of the functionality of many successful web apps can be replicated in a spreadsheet, but the added value of the time savings, improved functionality and simplified workflow make the web app worth the price (although not necessarily critical).