I don't live in 'Mayberry'.
I live in a very normal and very modern place. It's not a 'small town' either. It's completely landlocked, with the big city boundary on one side and other old suburbs on the three others, has lots of high rise residences as well as single family homes, has a very urban feel, many offices and plumbers/electricians/carpenters/upholsterers/other workshops, small industry in the shape of a cement works, body shops, car hire places, decent nightlife, very mixed population from pov of income, ethnicity, national origin, lots of churches of all stripes, synagogues, shops, a few parks and playgrounds, a municipal skating rink and two outdoor municipal pools. There is also a library and a few branch libraries and there are several places where skateboarders congregate. There's a hill for sledding that gets a lot of winter use and two small hospitals. The population is about 57,000 and will rise to about 100,000 in the next ten years as there are several high rise developments being built.
There is hardly any graffiti. Weirdly, local teens don't seem to feel the need to deface property. Maybe they don't sense much hostility to fight back against. What 'counterculture' there is tends to be channeled into very arty avenues. There is hardly any interpersonal crime. Muggings and burglaries are big news if they happen.
Millions of people live their lives in places like this and bring up decent, respectful children in them. They are not 'fantasy utopias'. Those millions of people don't take refuge behind tired old platitudes that they don't really understand such as 'Good fences make good neighbours' and 'There are disturbed people around, and there always have been'.
They make the effort to introduce themselves when they move in and to greet newcomers to their neighbourhood. They take the time and go to the trouble to get to know their neighbours. Above all, they understand that they are responsible for the quality of their own lives, and they make the choice to be net contributors to a sense of community. They do not indulge in the sort of anti-social attitudes that are so acceptable in Britain that the phrase 'fantasy utopia' is used to describe perfectly normal lives elsewhere, and eyes are rolled at the idea of knowing your neighbours.
Why would people piss in someone else's garden, Littlecandle? Do you think this happens much? Do you believe that the only thing that is stopping people from camping in your front garden, pissing on your bushes and leaving little surprises for you under your roses is your fence or your front garden wall? Do you really think people would tramp through your house and take over your bathroom if you didn't have a barrier out there against them?
How sad if so.
Your garden is not private if other people's balls are flying in. If you want to keep it private, a no fly zone free of all flying intrusions, then you should put up some sort of high net.
Trying to keep it 'private' when you most likely live at close quarters with other people who are just trying to enjoy their own lives and little patches of garden is clearly an exercise in futility, bordering on an exercise in insanity.
The question should not be, 'How best to deny reality?' Or even, 'How best to teach the brats next door a lesson with the utmost degree of passive aggressiveness?' (This is clearly a priority among those who are pooh-poohing practical solutions).
If you're reasonable and you accept reality, and if you want to contribute to the general good vibe of your neighbourhood (this may be asking too much, I realise) the question morphs into, 'How can we all live together as amicably as possible?' Sticking to the philosophy of 'My home is my castle'/'We will fight them on the beaches...' will only net you an ulcer.
You will continue to live in your own angry, resentful and - you should face it - fear filled little mental world in which you feel you must man the barricades against the 'disturbed people out there' who might torture a rabbit to death, or maybe
even give you a cheerful wave as they find their own ball and skedaddle back over the fence with its posts that are sturdy enough to nail slats to (yes indeed Francis, they are pretty sturdy-looking, aren't they; they're just like the posts of my alien and completely different American fences in fact...)
Allowing children access to your garden to get their own balls back solves everyone's problems with one fell swoop. It's what you might call an elegant solution.