Every release or two, Microsoft creates a new file format
Microsoft opened the barn doors when they pushed to have the office format declared an Open Standard. They were very nervous that other file formats would be declared the new preferred open format by governments and organizations trying to get away from closed, undocumented, and proprietary formats. This has allowed other office suites to accurately read and write documents in Microsoft's formats. If Microsoft now tries to change their format again, without documenting all the changes, they risk having the Office 2010 format declared the only supported file format users are allowed to use by many companies. Microsoft's last couple of releases have done nothing but change the UI or licensing terms without adding anything substantive.
The horse has left the barn and Microsoft will have a devil of a time getting it back in.
Stop spending trillions on "defense" and you can take care of the sick and elderly, educate the young, feed the hungry, pave the roads and repair the bridges., and still have enough left over to explore space.
Without that money spent on defense, you wouldn't have any sick, elderly, young, hungry, roads, or bridges to worry about.
"When anyone says `theoretically,' they really mean `not really.'" -- David Parnas