As usual, mega-spoilers.
The first three rules of writing fiction are: 1) Show, don’t tell. 2) Don’t indulge exposition. 3) Seriously, exposition just comes across as lazy.
With this in mind, everything’s a trade-off. There’s a really good reason to write a story or series of stories about a bunch of characters struggling against forces or a history they don’t really understand, and learning this history becomes central to their goals of victory, self-awareness, or survival. It creates a lot of suspense—-are their decisions made in ignorance good ones? what is the mystery? will the writers make the reveal live up to the suspense? I also think audiences like these stories because they reflect that part of the human experience where we feel thrust upon Shakespeare’s stage, but we don’t have lines and we don’t know what came before, and so we have to learn to improvise. Writers both of pop culture products (Harry Potter) and of high art-style works (Toni Morrison in “Song of Solomon”) have used this story to great acclaim.
But there’s major pitfalls to this kind of story-telling, too. First of all, it’s nigh impossible to get around the suspension of disbelief issues that arise when some characters know the truth, or at least more of it, but they conceal the truth from Our Heroes for reasons that don’t ever make complete sense. The Harry Potter series suffered tremendously from this issue—-there came a point where the adults holding the truth from Our Heroes on the basis that they were just children didn’t make any sense, because Our Heroes had proven time and time again that they had the maturity and experience to deserve the truth. “Battlestar” avoided this trap by making the one man who knows a complete control freak who orchestrated the Final Five’s ignorance to punish and control them. But the other danger is that, after each new revelation only expands and deepens the mystery, you get to this point where the mystery is so complex that you can’t reveal it all through plot machinations and have to resort to exposition.