The author still has to know what's inside the gaps. Also, the gaps have to look coherent - they can't appear to the reader as noise, or it simply won't create the right impression, no matter what.

You may be overanalyzing here. I've never published anything that I would've considered sending in to a science fiction magazine - maybe I'm holding myself to too-high standards, but still, it's not like I'm outlining the plot and building character sheets. My goal in writing online fiction is to write it quickly so it doesn't suck up too much time (and I quite failed at this w/r/t Three Worlds Collide, but I never had the spare days to work only on the novella, which apparently comes with a really large productivity penalty).