You may not realize it, but... data you create or receive are, in a sense, held hostage by the program or programs that understand that data. If your data are stored in a proprietary format, your data are not fully under your control.
Businesses may do as they will; for the most part, one can choose not to deal with a particular business. Government, however, has a monopoly on coercive force. If government decides to only provide data in a proprietary format, or to only accept data in a proprietary format, it forces us to patronize the company that provides software that handles that format. That is fundamentally wrong.
Therefore, some governments have passed or are considering laws requiring open, non-proprietary data formats for data files they create. That is not going over well with the companies with proprietary data formats, and is leading to things such as this (via Slashdot):
A legislative staff employee who would lose his job if he were quoted here by name said, "By the time those [Microsoft] lobbyists were done talking, it sounded like ODF (Open Document Format, the free and open format used by OpenOffice.org and other free software) was proprietary and the Microsoft format was the open and free one." Two other legislative employees (who must also remain anonymous) told Linux.com that the Microsoft lobbyists implied that elected representatives who voted against Microsoft's interests might have a little more trouble raising campaign funds than they would if they helped the IT giant achieve its Florida goals.(I added the [Microsoft] to the quoted text.)
So, if you use Windows, and especially if you use Microsoft Word, that is what you are implicitly supporting via your purchase. Please give serious thought to switching to OpenOffice or another word processing package that supports Open Document Format if you use Microsoft Word, and consider switching to Linux if you use Windows.
For more information, check out Slashdot or Linux.com. Groklaw has lots of information about Microsoft and Linux (and about SCO's attempt, partially funded by Microsoft, to kill Linux via bogus claims of copyright violation), and I expect they will cover this issue shortly.