I've never been bitten by a dog. But I've had enough close encounters to be nervous of them, or rather should I say, careful with them. (I'm sharing this after reading Rudi Massyn's article, by the way)
While still a schoolboy, a dog charged me on my bicycle. I was going downhill, so I could bolt, but the dog caught up. It ended under my front wheel, I ended up going head over heels over my handle bars, and hit the deck on a nice soft tar road. Luckily for the dog it suddenly vanished. I had little black stones stuck in the skin of my knees, but was otherwise unscathed. Dogs often chased us on our bicycles!
In another incident I was taking a short cut to the Farmers Hall, over a patch of veld. A pack of about five brutish dogs, mongrels consisting of all the largest breeds on the planet, suddenly charges out of an unfenced garden about sixty metres away. I sensed a horrible death looming, and started sprinting. I had a good 100 meters to go to get to the main road where I felt I may be safer. It was a lost cause. They quickly caught up with me, the whole pack, and at that moment I tripped and hit the deck. The veld had been burnt recently, and was kind of spiky. I expected the pain of teeth ripping into my flesh ... but when I got up the dogs had all U-turned and were heading back home. Maybe the owner had called them? I was dirty and a bit sore from the fall, but that's it, I lived through it. Weird.
The closest I think I came to being bitten was the fault of a mate of mine. He had the hot's for a girl he had met one night, the girl lived on a farm some 50 k's from us. He hadn't quite got the address right, so we ended up going from farm to farm asking the owners if they knew where this girl lived. Not a good idea, a lot of farmers have the meanest dogs on the planet, their security due to their isolation. We drive up to this house, no fence's, and this lady is in the garden. We get out the car and walk towards her, about twenty metres from the car we notice the brute lying on the verandah behind her. We ask the lady about the girl, she looks at us suspiciously and says no, never heard of her. Not very friendly. I think we looked a bit "rof". So we say thank you and turn back to our car. The brute suddenly ignites and bolts at a frightening speed making the most unpleasant gurgling murderous sounds. Adrenalin kicks in and we bolt. I promise you, as I slammed the car door, the brute hit the side of the car, spit all over my passenger window. Mayi ba bo!! Close. We even drove fast off the farm. (Oh, we did eventually find the girl for anyone interested)
I must admit, I've only ever been attacked when passing a dogs "territory", or entering it. I find unleashed dogs on the beach no threat, unless I have my dogs with me. On the beach, I'll take my dogs to somewhere I can't see any other dogs, then I let them off their leashes. They can't really enjoy the beach on a leash. My dogs don't bite humans, there is no question about that. (Unless perhaps I am attacked by a human, they may bite then, but won't be capable of doing much damage) Unleashed dogs are dangerous when they are near their owners and surprised by humans. Well socialised dogs like mine will never attack another dog, but will approach other dogs. If those dogs are on leads they will be defensive and there could be trouble. So we only unleash our dogs in the company of others if the other owners communicate that its ok, their dogs are socialised. If my dogs are approached by a dog "on the loose", I let my dogs off their leads, so they can meet in an unstressed situation. I force myself to relax, and just let them get to know each other. If us as humans are stressed, the dogs pick it up and want to barney. This has never happened, a bit of growling and stuff, but that's when you need need to ignore them, they're just trying to secure themselves. A few moments later they're all best mates, playing and running around together.
My most amazing dog experience was visiting a park near Melville on a Sunday morning. The entire park was filled with hundreds of unleashed dogs and their owners. Everyone was relaxed, there were people running, cycling, all the dogs just behaved and got on with one another. It was really cool.
So my long winded point is, to leash or not to leash revolves a lot about how you understand dogs generally. It depends on how well you know your own dogs, it depends on the situation. A bit of common sense also helps.