Microsoft typically tries to settle such cases, and tried to settle this one, too, sources told Network World. i4i originally sued Microsoft for infringement over a method of parsing XML called "custom XML" in 2007. On May 20, 2009, i4i won a $290 million judgment against Microsoft, which included an injunction to stop selling Word.

But at some point, Microsoft was no longer interested in settling and instead launched an all-out fight. It chose to fight even though the specific disputed technology is no longer at issue. It has long since been removed from Microsoft Word. The money at stake, while not trivial, isn't a backbreaker for the mighty Microsoft either. In 2010, the and had reported payouts of nearly $2 billion from losses of patent suits (which included the i4i $290 million).

Microsoft chose to fight even after it lost an appeal with the Federal Circuit Court, which i4i calls the largest patent infringement judgment ever upheld by the Federal Circuit. And Microsoft was twice unsuccessful at getting the patent overturned by a re-review of it by the U.S. Patent Office.

Microsoft doesn't automatically apply to the Supreme Court for all lost appeals. This is only the second civil case Microsoft has ever argued in front of the Supreme Court. (The first was also a patent case, Microsoft v. AT&T in 2007, which Microsoft won.)

"The day that you learn they have taken your case is a very good day. It calls for celebration because a tremendous amount of work goes into the effort to get to the Supreme Court. The vast majority [of appeals] are denied. It is very exhilarating," Culbert described.