Even in sandbox RPs, there always needs to be a motive of some sort, or more relevantly to the central question of this thread, a central plot line that the RPers can base their stories around. As an RPer, how tight to you like to tie your own character in with the bigger picture or central plot? Do you like to be the son of the main bad guy tyrant who's oppressing all your friends, or do you like to be that one old lady who created the potion to keep everyone alive in that one fight against the kid with a stick? As a GM, how much do you like the filthy RPers messing with your precious creation and getting tangled in the web of plot you've created? Do you like them to touch and mould, or do you prefer them to watch, admire, and merely be affected by it?