In agriculture, a monoculture is the practice of relying on a very small number of genetic variants, or cultivars of a food crop for commercial agriculture. In essence, what it means is that by using a very small gene pool with little variance, an agricultural blight could swing by and wipe out the entire crop as the similar genetic makeup of these crops will render all of them susceptible to the blight. This, as you can clearly see, would be catastrophic to our food supply.
A similar situation does exist in ICT, as famed security expert Dan Geer has warned. By relying on a monoculture, we're making ourselves susceptible to widespread virus attacks. Dan's warnings however have taken a new twist with the Backdoor.Ginwui virus. The twist is that the virus is carried not by an executable program, but rather by the Microsoft Word document format, and the virus exploits a vulnerability within Microsoft Word itself. What is interesting is that the same virus has no effect and is benign on other programs which read Microsoft Word, like StarOffice and OpenOffice.Org.
This is strong testimony to the fact that genetic diversity, be it in agriculture or computer science, shields us from events which could catastrophically wipe out life. With a standard like ODF being supported by both closed source programs (StarOffice and IBM's Workplace Managed Client) and open source programs (OpenOffice.org and KOffice), the genetic diversity would mean that a virus carried within the document format will not affect all users of the format but only specific users of a program.
With more office suites using ODF, there will be greater genetic diversity. With this, our risk to genetic viruses, greatly decreases in a multicultural world.