The Economist writes:
The threat to Microsoft comes from online applications, which are changing how people use computers. Rather than relying on an operating system and its associated application softwarebought in a box from Microsoft, and then loaded onto a PCcomputer users are increasingly able to call up the software they need over the internet. Just as Amazon, Google, eBay and other firms provide services via the web, software companies are now selling software as a subscription service that can be accessed via a web-browser. Salesforce.com, the best known example of this trend, offers salesforce management tools; other firms offer accounting and other back-office functions; there are even web-based word-processors and spreadsheets. This lowers the economic and technical barriers to entry for firms wanting to compete with Microsoft, as well as diluting the advantages the firm gets from controlling how the computer works.