Format wars are not uncommon in the technology world. We had format wars with Betamax versus VHS in the 80's and more recently the Blu-ray versus HD DVD format wars. Another format war is brewing in the movie theater industry that could spill over into the home as well.
The battle is over what 3D system is most popular and what type of 3D glasses are used. In 3D systems today, there are both passive and active glasses. The active type of glasses are reusable while passive glasses can simply be thrown away or recycled like those used by RealD that many who say Avatar are familiar with.
The New York Times reports that the battle over the type of glasses used in theaters is brewing with some theaters backing RealD and others going for technology like XpanD that uses 3D glasses that have to be cleaned and reused. From a film watcher perspective, I would certainly prefer glasses that are one time use. The RealD 3D glasses reportedly cost about 64 cents per pair. My local theater charges $2 extra for a 3D film so they are certainly covering their cost. The XpandD 3D glasses are cleaned in an industrial dishwasher. The type of glasses won't be as big an issue inside the home with 3D content coming home in 2010.