As we noted above, many files are closely related to particular applications. You often cannot effectively open or manipulate a file except with the application that created it.
There are obvious solutions to eliminating application dependencies, all of which are problematic. One solution is to combine the file with its application. So every PowerPoint2 document also includes a (platform independent) version of PowerPoint viewer. This result consumes disk space with many useless replications of our application. A slightly better approach is to put one copy of the PowerPoint viewer on any device that contains a PowerPoint file, but that still is intensive.
The UNIX solution of fairly generic text files softens the problem but does not solve it. We could, for instance, edit the source files for this paper with a range of applications (emacs, vi, sed and awk are obvious examples). But trying to format the source using groff instead of LATEX would be problematic on a deadline.
New ideas are needed in order to make advances in this area.