So I just got done reading Kwame Opam's post on Rey's possible origins in the Star Wars Universe,
and I guess I am scratching my head. I get a lot of what Kwame is saying, and he seems to be versed in the Expanded Universe, but there was something that perplexed me: "instead of everyone having access to the Force, you suddenly had to be born with it."
Having watched the movies, and read a few of the books, I thought that was always true of the Force - it was something you were born with. Now, I get he wanted it not to be some family bloodline thing, like only Skywalkers can be jedi, and I think random people can be instilled with the force, like some people have blue eyes. It can be something with heredity, like Skywalkers are more susceptible to have children who are one with the force, but there is no guarantee. Or like two short parents can have a tall child - someone with no history of force in the family can be born with it.
BTW - I have two theories on Rey's parentage. One is that she is Luke's daughter, but that Luke never knew she existed. Her mother had her after a chance meeting with Luke. When she heard of the slaughter of Luke's jedi academy, or some rumblings about how people were after anything Skywalker, she went to hide her daughter on Jakku, then misdirected their chasers and was kept from returning.
Another theory, which would play with the whole Darth Vader/Luke Empire thingy, Rey is actually an experiment to resurrect Darth Sidious by one of the remnants of the Empire. She was imbued with his force, but one of the scientists who helped create her and began raising her turned on the project and making her dark, and ran off, hiding her on Jakku (alternative to this, it is all part of the resurrection of Darth Plageus, who could create life from midichlorians to escape death itself).