At the Rocky Mountain Fiction Writers Conference, we did a session on short stories. Lesley had the mic right then, discussing elements. Her mention that the story needs a protagonist, a character of some sort, got a laugh.
I had two stories in my last round of slush reading with no protagonist. No character. They weren't stories; they were vague summaries on the state of some world, the sort of rambling a writer might do as a world building exercise and then file away and never look at again. In short, they had no character, so there was no drama. No drama, no story.
I think I can safely speak for all the editors at Electric Spec, we require a character in each of our stories.
Some people think characters and plots are a chicken-or-an-egg kind of deal; some stories certainly reflect that line of thought with cardboard characters. Some people just think up plots first and others think up characters first; process seems to direct which side of the fence they sit on.
But picking a side of the fence is a colossal cop-out.
Sure, events can happen without a protagonist: worlds can form, glaciers can move, bombs can blow up nameless people. But they have no power, no oomph, no drama, without a character.
And characters can do stuff, yeah? They wander into vignettes, have interesting conversations. But without the structure of a plot, a plot that can only happen to that character, it has no meaning, no drama...
Mutually dependent? I'll raise you a thousand. Characters and plot are so tightly woven in good stories it can be tough to see where one picks up and the other leaves off. It could matter less which a writer dreams up first, but they'd better, at some point, become equally as concerned with the other, or their story will suffer.