Just remember if you go out of your area that in many places 2 abreast is totally legal, so before you condemn cyclists know the local laws. Out here in Seattle our laws read no more than two abreast when riding in areas not specifically set aside for cyclists.
Though some may find it annoying to see two cyclists abreast, around here where few roads have a wide shoulder, if any at all, one cyclist positioned safely in the lane should take up pretty much just as much space as two cyclists riding closely abreast. (occupying about 1/3rd of the lane). As a result, two should not necessarily be harder to pass than one.