It always shocks me when people are oblivious and don't ask before approaching a dog. I don't care what dog it is, ASK!!!! Yesterday I was out with my daughter and Penny for lunch; Penny was being extremely well behaved lying quietly beside the table. Several people came by with their dogs on EXTENSION leashes, EXTENDED; and allowed their dogs to just wander up to Penny. Lucky for them, Penny is fabulous with other dogs, but what if she wasn't? One woman had a little micro dog on an extension leash that ran right over and gave Penny a blast, all three pounds of it. Penny just looked at it like it was crazy.
Do we expect our children to interact with all other children? Do you want to interact with all the people who are passing by us at the beach, mall or restaurant? NO! Just because I am out in public does not mean that I want to talk to the people sitting at the table beside me and just because our dogs are out with us does not mean that they want to talk to any other dogs. If your dog wants to talk to all the other dogs that they come across, fine, but ASK first.
The same rules apply for children and dogs, ASK first. Just because a dog looks like a big friendly fluffy guy; does not mean that he is friendly at all. He may be friendly with some people but not others; perhaps he likes dogs but isn't keen on people, you never know. You should NEVER assume anything; especially approaching, interacting or touching a strange dog.
All dogs are different, just like us. Even when you do ask, you might not get the correct information. I don't know how many people say "oh yes very friendly" right before the dog snaps. Along with asking you have to read yourself. From a great deal of experience comes the realization that most people have no idea.