An a priori rejection of miracles?

I uploaded a short Youtube video (rather than writing a blog post) concerning miracles.

Here's the video description:
Do atheists/skeptics/secularists have an a priori rejection -- one before any sort of experience of investigation -- of miracle claims? If so, is this justified? Is this a bad thing? How do 'believers' of all stripes justifiably jump from "I don't know/I can't explain this" to "it's a miracle" ...and then ascribe the miracle to a specific source? I'm willing to accept miracle explanations if given good reasons, but what I have heard so far has been very insufficient.