Probably a little of both.
Thats my opinion that I have formed over the last several years. It seems to me that unlike any other domesticated animal, dogs have a very special relationship with humans (NORMAL humans, not counting those who hate dogs because of some misguided cultural ideas, if ya know whom I mean, much misguidedness in that culture overall, but I digress).
We co-evolved over the last many millenia, and the more I learn about dogs, the more I am convinced that they are made for us, and us for them.
The Duke University Canine Cognition Center has uncovered, or rather, re-covered some amazing things about dogs and their ability to "get" us. Things even other higher primates cannot do. We are truly meant to be together.