I would rather all dogs be on leads in public places. I do think that parks should provide a fenced off area that is specifically for dogs to be let off the lead though.
I am a dog owner, and have a dog who seems to have an invisible sign on him saying "come running up to me", because every dog that is off a lead seems to make a bee-line for him, and he is nervous of other dogs (after being badly attacked a few years ago). I keep him on a lead at all times in public, but we avoid the parks now where there are so many dogs running around off lead who want to charge up to us. I dont care how "he is friendly, dont worry".. my dog is nervous..he doesnt want other dogs bounding up to him.
We have spent lots of time and money with behaviour therapists to try and get him, and us, more confident, but he is still wary of any dog he doesnt know.
My "vicious" beast is on my profile too. Be warned... he is a staffie. 
On the other hand, my dog is the most calm dog I have ever known. I have friends with young children who love letting them get used to dogs using my dog as a first go.. because he will sit there, and doesnt jump up, lick, or mind being prodded. (Always done under supervision before anyone worries).
We take him out wherever we can, he sits under my chair most of the time, and is much less trouble, makes less mess, and is a lot quieter than any child!