Because MS Office will screw up XML . .
. . it will be incompatible with any but Microsoft applications and servers, locking out other application servers. The servers in turn, tuned to do XML the Microsoft way, will lock out StarOffice and any other standards compliant products.
Microsoft has an army of big consulting firms and integrators (some of whom they have a substantial cash investment in to assure the "right" recommendations), as well as tens of thousands of software developers, VARs and smaller consultants, all being hussled into the .NET way of integrating business processes. This vast army knows only the Microsoft way, and will consider no other.
The best thing about this all pervasive force is that it does its work silently and invisibly. Companies are locked into One Microsoft Way before anyone realizes anything is happening. Against it, the efforts of IBM and Sun are minor, and Open Source doesn't show at all.
Once a company is integrated wit BizTalk Server, they force all their suppliers to be compliant. Proclaiming that Microsoft products "violate standards" has never worked in the past, and it's going to take a hell of a lot of effort to make it work this time. "Conform to the Microsoft way and you don't have to worry about 'standards' at all."
The one bright spot is that Microsoft's moves to expand into new markets are offending major customers who have one hell of a lot more business smarts than anyone in computers or software has ever had - like Sony. This accounts for Sony's move to StarOffice in Europe.
[link|http://www.aaxnet.com|AAx]