Regina is the product of a lot of work by Rumple. If I have been reading all the clues right it seems that Rumple has been working a long time to get his curse enacted. I believe that Regina is the child that was promised to Rumple and loosing her was part of the plan. He set the dominoes up so that Regina would use the curse. I am also starting to believe that Rumple was the person who spooked Snows Horse. That one event proved to be the driving point for Regina casting the curse. I also like the fact that while Rumple helped create the evil Queen, it was the Queen who hid his one true love from him.