Microsoft has been in legal trouble from quite some time as it was found the some technology used by Office products for parsing XML content in its Office Open XML files (docx, xlsx, pptx etc.) infringed on i4i's copyrights.
Microsoft loses patent appeal against i4i
The technology, which allows for manipulating the architecture and the presentation of a document separately is present in all Office application including Word, and Microsoft was supposed to stop sales of its products by January 11th. This technology has been present in Microsoft Word since it was introduced in Microsoft Office Word 2003.
Microsoft claims that the technology isn't present in the Office 2010 betas, and they will be moving fast to remove the offending features from their Office 2007 products to ensure that they can continue selling their products sans the custom-XML features after January 11th.
In any case the only person affected in this is Microsoft, as customers who have already own copy of Microsoft application with the infringing features can continue to use them. In return i4i will have to be remunerated with a sum of $290 million.