Warren Buffet is a better example of "wealth" gone FOOM.

Microsoft went FOOM, but it wasn't its money that went FOOM. It was MS-DOS that went FOOM. Many of Microsoft's other products were only as successful as they are because they were tied to MS-DOS and Windows. For example, the reason everybody uses Microsoft Office today is because, years ago, Microsoft charged PC manufacturers less for the Office + Windows bundle than for Windows alone. Everyone's PC already had Office installed when they bought it, so nobody had to go buy WordPerfect to do word processing or Lotus 1-2-3 to do spreadsheets. And then, once vendor lock-in took hold...