In a perfect world, from my point of view, we wouldn't allow visitors at all. We catch way more flak from visitors than we do from registered guests. First, we are very firm on the policy of visitors checking in with the office before entering the facilities. This is for security as well as giving us a way to identify the owner of the vehicle who inevitably parks in either the middle of the road or in another guest's site.
We also have a policy of not giving out the site number of a guest without that guest's permission. I don't have any idea of the liability we would incur if I gave out someone's site number to a vengeful spouse, a repossession agent, a stalker or an annoying relative that our guest was trying to get away from for a weekend and I am not interested in finding out. When we refuse to give out site number or allow that visitor to enter the park without the consent of the guest, all hell often breaks out.
Then there are the situations previously addressed. Family reunions, a big group friends camping in the wilderness who get one site and then parade a couple of dozen people into the showers, people who want to use the parks's entertainment amenities etc.
We actually do not charge for guests. If the guests stay overnight, we consider them occupants and charge accordingly. Instead, we just vigorously monitor, enforce and sometimes invoke the the golden rule of "we have the gold therefore we make the rules" to keep everything moving as smoothly as possible for all of our guests. I am not interested in getting $5.00 from a guest, instead I want to get several hundred dollars each from the satisfied customers registered at the park who stay longer, return in the future, write great reviews and otherwise enjoy their stay. We are very diligent in ensuring there is not a guest who abuses the visitation rules and intent and therefore makes the park less enjoyable for everyone else.
However, all of our policies and procedures are predicated on the fact we are not located in areas where our paying guests have large numbers of visitors. For those parks, our rules and policies would not work and we would have to re-invent ourselves. In those types of parks a guest fee may be a necessary part of that reinvention.