On the Community Moderator Election Site it says that there are only three moderator spots available. Why only three? Wouldn't it make sense to have, e.g. 5 moderators?
Ignoring for the moment the long-standing practice of Stack Exchange staff to appoint three moderators to each site and grow the number as necessary, we can discuss the topic on having as few moderators as possible.
Why not more?
Let's take a look into the other extreme, where everybody, or pretty much, have the same powers as moderators:
- Controversial questions would be subject to "mod wars" with closing, reopening, locking, unlocking, protecting and deleting.
- Consensus is much more difficult the more participants there are -- a situation not unlike herding
modscats. As they say in Sweden, tastes and opinions are like backsides -- split.
- The more "superusers" there are, the greater the possibility one or more would go rogue. This is definitely a stressful event for the community, and AFAIK it only happened once or twice in the whole SE network. It does cause unnecessary waste of time and effort for a lot of people when they should be focusing on community growth, not bickering between themselves. There's a reason why direct democracy works only on a tiny scale -- people in general are just too untrustworthy.
Moderators are supposed to be "exception handlers", stepping up mostly when community can't or won't correct itself. The bulk of the site governance is supposed to be performed by the users with high enough rep. There are a few mod-only tools which are sparingly used, like the ability to suspend users, to completely remove posts or merge tags.
It's hard to give a justification why three seems to be the magic number (perhaps a SE representative could shed more light?), but it's easy to see why it's the minimum possible to have some sort of balance of power -- with three, it's easy to build consensus and resolve issues with two possible outcomes without concentrating the power into a single person. Granted, you have the same possibility with five, but there's not much added benefit of having more moderators. Moderation on most SE sites, and in particular Travel-SE, is not too bothersome, I gather -- we rarely get questions that split the community apart, spam is so rare as to be treasured when occurs, and users behave themselves and do not vandalize.
You can think about it in another way -- if you have a limited pool to choose objects from, and you rank them according to some arbitrary characteristics, necessarily the properties of the five best on average will be worse than the properties of the three best.