Yes. But, what if everyone did it? 
If “it” means “sex”, I’m all on board!
That Starbucks in Picadilly Circus has no idea what it’s in for.
This.
Has anyone ever actually been fined for taking a single pebble off a beach?
In the case of pebbles on the beach, I would keep a “Do Not Remove Pebbles” law on the books, but enforce it only if and when pebble removal becomes a problem. Start by posting friendly signage and if it appears the rate of pebble removal becomes problematic, post a less friendly sign, then another even less friendly sign if needed. Find the level of enforceability and signage tone that results in a sustainable pebble population.
- Help Keep Our Beaches Beautiful
—please don’t remove pebbles.
- Please Don’t Remove Pebbles From the Beach—it’s the law after all.
- Do Not Remove Any Pebbles from the Beach! —violators will be prosecuted!
- Don’t Even Think About Removing a Pebble!!!—violators will be electrocuted!
Here in Florida we have a similar problem with people harvesting sea oats and sea grapes from beach dunes. Here is the statute (which is rigorously enforced):
In other contexts, it seems to work fine to just tell people not to be unreasonable or to allow a ‘reasonable amount for personal use’. I realise that might seem like a hopelessly vague concept to some people reading this, but there are already implemented rules like this in the UK, and they work as well as anything else would.
Not that I can see. But here’s something similar.
These are problems generally solved by economics. We don’t need to ban people from going into Starbucks because the market will correct in one of several ways - 1) Starbucks can raise their prices so fewer people just show up 2) they can increase capacity or open more stores 3) they can do nothing and let “first come first served” sort it out.
The pebble problem is an example of the “tragedy of the commons”. The beach is a shared resource so theoretically anyone can just pick up some pebbles and walk away with them.
So the “if everyone did it” argument generally applies when there are no market forces or other mechanism that would prevent everyone from just up and doing something until the resource is depleted.
There are limiting factors on the number of people likely to visit any given stretch of coast in the UK - ease of access, available parking, distance from population centres, weather, aesthetics of the beach etc. The question isn’t whether anyone theoretically can, but whether everyone practically will. They won’t.
How fast do the pebbles get replenished?
Constantly, from longshore drift, ultimately coming from erosion of cliffs way along shore somewhere. That’s basically where beaches come from in general.
So does a person picking up a pebble on the beach meaningfully contribute to depletion of the beach, leading to a greater level of erosion? Mathematically, it can’t be argued to be zero, but neither can the effect of simply walking on the beach. If you want to ban people picking up a pebble on the grounds that it contributes to coastal erosion, you have to ban people from going to the beach at all, because any disturbance to the beach - even a footprint - has a nonzero effect on erosion.