Why are the Black Riders Rebelling? is the King a crappy King, or just kind of out of it, are they just anarchists?

Why are people all of the sudden finding dragon eggs? are they just falling from the sky like rain, like it's a common thing, like it rains dragon eggs every tuesday at 7:35, or is it super rare, somewhere in between?

I realize this is Free, so maybe I'm asking a few too many questions...