This is something that I think all have wondered about. We know that Hoid was there at the time of the breaking, but we also know that while the first 16 shardholders were from the same planet as him, Hoid did not take a shard. There has to be a reason because (as Sazed proved) it's possible to hold more than one shard, so why didn't one person take them all up? Why split it? This makes me wonder how some people ended up with shards at all. We know that Ati was generally a nice guy, and he ended up with Ruin, but Rayse was a horrible person, and ended up with Odium. This makes me question if the shards themselves chose someone, since I could see Odium choosing a hateful person, but why would Ruin choose someone "nice" for destruction? However, reverse the same logic and it doesn't make sense if someone was "handing them out" since why would that person give Odium to Rayse?
I seem to remember a quote from Mr. Sanderson saying that there was a "force" that was opposed to Adonalsium, and that said force is still "out there". Could it be influencing people? Maybe just trying to sew chaos?
Too many questions...