Bill, if every sheepdog which had tasted blood was put down, very few if any would still be alive and chasing sheep in New Zealand. And probably Australia. They regularly lose their cool and nip the sheep, some harder than others. The best cure for that, especially if you are working sheep with them in the yards, is a four-foot length of alkathene pipe.
Dogs are put down every week in New Zealand for molesting sheep. The vast majority of these are stray city dogs which have gone walkabout and discovered sheep - and their propensity to run away from dogs - for the first time. The range of breeds when one dog acts alone is usually in the German shepherd/rottweiler/doberman area. This is not a rule, however. Labradors, retrievers, terriers and spaniels have all been guilty of it. When a pack of dogs goes rogue and starts molesting sheep, even poodles and pomeranians have been involved. And even Keeshonds. The number of border collies involved is probably in proportion to the number of pet collies that exist as a percentage of the pet dog population. Farm dogs very rarely molest sheep off their own bat, although it is common enough. A pack of farm dogs would rather fight among themselves than chase sheep off duty. And frequently do unless the most aggressive ones are confined when they're not working.
Pure border collies as sheepdogs are reasonably rare in New Zealand. There is nothing magical about the breed, although it's a good start. Farmers will breed a good bitch with a good dog regardless of the breed. Collie ancestry is usually present and sometimes appears to be the dominant influence, but mostly they'd no more be able to claim a border collie pedigree than I would. My father in law was a noted dog breeder and handler when he was farming, and most of his dogs were real mongrels and looked it.
In New Zealand and Australia there are three "classes" of sheepdog. These are the eye dog (as you described), heading dogs (which are good at rounding sheep up and directing them en masse to a certain point and, usually, working the sheep in the yards) and huntaways. Huntaways are the "lone wolves" of the sheepdog world. A huntaway is sent up the hill to bring down sheep which have avoided being rounded up by the other dogs. They quite often go considerable distances out of sight of the musterer, and they have to be trustworthy. Of course, not all of them are. Stories about the judgement and sheep-herding ability of huntaways are the stuff that books are made of, literally.
Your link was interesting enough, but nothing in it was unique to border collies. I know a Jack Russell terrier which is as smart as a whip, although I won't bore you with dog stories. My first Keeshond was as cunning as a shithouse rat, and they're not notable as an "intelligent breed". My current one, however, isn't frequently called "Shitfer" for nothing ...
