Rodney hits it on the nail when he says the city, for fear of liability, may just elect to close the fishery as the cheapest way to solve the problem. Remember, compared to the non-fishing public, the anglers are simply the minority. When words get out that an innocent kid or unsuspecting park walker just got his eye rip off by a fly hook while enjoying a leisure walk, what do you think the reaction of the public will be? They will be all over the city to shut out the fishermen so they can feel safe to let their kids run around in the park. They can simply stop the stocking and fishermen will be out of luck and who is to blame?
You also hit it right on the nail, Hook, when you say 'excluding the children'. But can we really exclude any one? In a lawsuit, there is no such thing. When a fisher's action can potentially harm a child, that action will be stopped, and when the action has caused harm with permenent damage, a lawsuit will follow and you cannot claim innocence that a kid should watch out for his own safety.
Even if the city or fishery posts a sign that says 'BEWARE of FLIES!!!' (

), a child, even a non-fishing adult, will not know what it is all about. Will a 3 year old read it and understand it? Will a non-fisher know that there is a hook at the end of that line which goes back and forth along the walkway? I doubt it. Perhaps that is the reason why they walk right into it as if they were blind, as you stated, Hook.
So shore flyfishermen should take the proper action to protect themselves from potential lawsuits and to protect unsuspecting pedestrians. The last thing we want is city/fishery closing down stocking of urban lakes because of some careless shore fly tossers.