It's not so much being overly friendly as not being cautious that I would worry about. Dogs usually have instincts when it comes to strange animals. They either back off or chase them depending on the situation. It sounds like your dog might not have that sense of caution.
I think it is a good thing that your dog is friendly with people. My previous dog, a Lab, was that way. She loved everyone. When I took her to the vets, she seemed to think they were all there for her enjoyment. She was great with kids and would let them do anything to her.
My Jack Russell is afraid of strangers. She's great with people she knows, but she is reluctant with others. I wish she had more of that friendliness in her. When we meet people on our walks, I have to warn them not to pet her because I don't want anyone getting hurt. People don't always realize that some dogs need to warm up to you.
