mete,
Only for rifles, not for pistols. For pistols, dominant eye really doesn't matter much -- just make the appropriate, minor modification to your preferred stance and you're good to go.
Also, just as some people might be more strongly left-handed or more strongly right-handed than other people, it isn't unusual to meet people who have a more strongly dominant right eye or more strongly dominant left than others. Not only this, but just as you encounter ambidextrous people when discussing handedness, you also encounter "ambi-eyed" people, who do not have a strongly dominant eye on either side.
All of these factors come into play when people select their preferred, default shooting stance with a pistol.
pax