It turns out that a debate over the proper combination of condiment and shaker has been raging for years, with no definitive answer in sight. Some say that tradition favors a salt shaker over a pepper shaker hole-wise, with many older sets featuring two pepper holes to four salt holes. Others make the ratio a little more balanced, with three holes for salt and two for pepper. In some countries, such as the UK, however, it is not unusual to find a salt shaker with only one hole and its pepper partner displaying four or more holes. Clearly, there is no universal standard at work here.
Some say that a salt shaker should have more holes because of its favored status as a spice. Many people tend to shake a great deal of salt on their food and only sprinkle a little pepper. Therefore, the salt shaker should have more holes in order to improve the flow, while a pepper shaker should do all right with fewer holes. Others say that it's not the number of holes that makes a difference, it's the size of said holes. Salt grains are thought to be larger than equivalent ground pepper flakes, so they should be put in a shaker with fewer, but larger, holes. Since ground pepper is lighter and dustier than salt, it requires more holes in order to flow out at a comparable rate.
As if this weren't enough fodder for the controversy cannon, there is the "too much salt is too much" argument. With a number of people who are already on, or perhaps should be on, low sodium diets, many argue that the salt shaker should contain the fewest holes in order to prevent overuse. Many people habitually shake the shaker without regard for the actual amount of salt escaping through the holes. Some conscientious family members have even been known to use superglue or other means to reduce the number of available holes. Pepper, on the other hand, is rarely subjected to these types of dietary restrictions, so it can be safely put in the shaker with the most holes.
Many restaurants use disposable pepper and salt sets in order to reduce the need for periodic cleanings, and these shakers do appear to favor salt over pepper, at least by a hole or two. Some shaker sets spell out the letters "S" and "P" to denote their contents, which appears to level the playing field considerably. Etiquette and household experts also disagree on the standard number of holes in shakers, leaving it up to a user's personal preferences. A number of food experts, however, recommend using a pepper mill in place of a shaker containing pepper of dubious freshness and quality. Some even suggest using a salt mill containing sea salt crystals instead of a shaker. While this method may not make an individual a hero at his local fast food joint or greasy spoon, it does provide an elegant answer to the shaker debate.
In short, if there are no other indications for the appropriate spice such as labels, initials or color cues, then people should feel free to put whichever spice they prefer in the shaker with the most holes. If they are not happy with the flow, then they can make a switch. As long the people who are using the shakers know which is which, then all should be right with the world, seasonally speaking.