<Snipped quote by The Harbinger of Ferocity>
I feel like if you can't explain it at the appropriate time and place and be able to justify your actions/reactions in the IC, this would be the wrong place to be writing. Show, not tell, as the say. However it's a minor if annoying point that won't tip the scales so this is just for the sake of devils advocate.
Indeed, many should be more than able to know where their character is rooted and whatnot. But when we, as a group, are attempting to steer the plot, it in my opinion be quite beneficial to know where the other characters stand and where they are coming from. For example, it might be easier to suggest a course of action that would rely on another character's connections if one knew of said connections. Speaking of OOC interaction of course. I would thus place my confidence on sharing the story of the individual, at least in broad strokes, rather than to leave it fully in the dark. Personality though, those details are less important to the building of the story and and a general, almost handwavy approach would not be questioned in my book.