My choice would be either Windows Word or Quicken. Most offices use Microsoft, and Word is what is used to draft letters and communicate, vis-a-vis, in the professional world. Without that medium, much business would be halted, companies would have to shell out a lot of money to move their business into the Mac, and smaller companies might not recoup. A lot of smaller companies who cannot afford that much out of pocket to buy several computers and to rig up a server might go belly up, paving the way for greater numbers of the unemployed, which might seriously unhinge the economy. As for Quicken, I know that it's one of the preferred program for accounting and recordkeeping. If it suddenly went 'Poof' one day, it would cause setbacks in larger companies who rely on it. Without that networked program to handle all the various financial transactions or ledgering, companies would have to go to an alternate source, have to revamp their whole accounting system. This rebuilding might cost the company a lot of unrecoupable time lost, which may lead to downsizing to recover that fiscal negative, which may add to the economy woes, and so forth.