I enjoyed this quote in Charles Babcock's Why Windows must go Open Source:
Microsoft's applications are vulnerable, as well. The proprietary file formats that have protected Microsoft apps have been offset by Office Open XML, the default format for Office 2007 and now an international standard.
So for the first time there are no real technical barriers preventing other vendors from playing in the end-user applications market, and competitors are nipping away. Office alternatives include IBM Lotus Symphony, Sun Microsystems Star Office and the related Open Office open source code project, Google Docs, Yahoo's Zimbra open source apps, and Zoho.
There still are, of course, non-technical barriers: Microsoft can outspend and outmarket and outstare smaller companies who hope to encroach into its share. These are not things that standards can address.
But what standards can do is help Microsoft move towards being a normal company, just another participant in vibrant markets; in many cases this will be a move from market dominator to market leader, which falls short of the druthers of many people that MS would disappear like a magician's assistant, but is not nothing by any means.
A standard like IS 29500 (OOXML) creates a level-playing field by providing information for symbiotic and competitor developers: it builds up the low ground. But there is also useful role in standards that slice off the high ground: IS 26300 (ODF) fits here: it creates a new market for less full-featured applications than an unstandardized market allows (and this will effect not only Microsoft, but also Word Perfect, and many Open Source applications too.)