Imaro
Legend
But, that's the problem. All of the things the players will interact with are separate and distinct from their characters or backgrounds for the most part. Even if they players read the entire campaign setting back to front, the odds that their particular backgrounds will tie to any specific element are pretty tenous. That spooky castle on the hill exists in the campaign world irrespective of whatever players or characters are brought to play.
To me, I'd much rather change the campaign world to reflect the characters. If they are playing a bunch of church knights out to slay undead Van Helsing style, then, fine, spooky castle it is. If, OTOH, they are all playing ninja assassins (shudder), then spooky castle isn't going to cut the mustard. Instead, it will be a living castle of someone they need to spy on.
Ok, I'm curious... what do you do if a player isn't ready or doesn't want to flesh their character's background out before you all get to playing? Do you force them to anyway so that you can tie them into your campaign (this seems more for your benefit than for the player)... or do you ignore them as far as tie-ins go (so then if you've done this what is the big deal about having pre-game connections and hooks.)?
A second point is that the PC's are only missing background until they interact with something or someone in the campaign... yet even with out the detailed, pre-written background there are ways to tie PC's into a sandbox campaign, it just takes some creativity and cooperation. One of the techniques I've used when running a sandbox is that the characters can interject a certain number of memories, flashbacks or dreams that can help tie them (with DM and/or tab le approval) into the NPC's/events/locations/etc. of the campaign.
Finally I think your example of the ninja and the spooky castle are exactly what I'm talking about. I think a story of a clan of ninja who enter a manor, for whatever reason, only to discover it full of undead and spirits could make for a fun and interesting adveture... yet by your method, you have automatically discarded it because it doesn't fit within your vision of a "ninja campaign"... IMO, it seems you could miss out on some cool adventures and plotlines because you are purposefully limiting yourself and your players. Like I said earlier your method may provide for a more focused game... but that doesn't necessarily translate to a more fun game.
People talk about this, but, IME, what actually happens is the campaign never gets a chance to gain any depth. The players are constantly trying to see what's over the next hill, so never stay in one place long enough to make any connections or whatnot to the campaign world.
I'm not trying to be snarky, but this seems to be a problem with your ability to run a sandbox... not with the concept of sandbox play (especially since you've fallen back on insinuating that people who have run these types of campaigns may just be talking but not actuallly doing).
IME, you have to create things that entice and present the opportunity for the PC's to want and create connections. I mean don't they have a home base? what are the politics going on within it and how do they affect the PC's? How do they uncover the locations of things without researching and/or interacting with those who would know more in their homebase? Do they seek out mentors and masters to train with? Henchmen or companions to adventure with? How about rivals that are seeking the same things they are?