I have most workers set to auto because i can't stand moving them around.
However, i do keep a bunch on manual.
I was building a wonder in a city and so had workers build mines on every square. After awhile i realized the auto workers were coming by and ripping up the improvements. I was too lazy to change all workers to manual...so it became a fight to keep the mines.
I looked hard at the larger map and suddenly realized the auto workers were laying down staggered and alternating rows of irrigation / mine tiles --regardless of terrain (edit: actually this is only true on grassland/hills. On desert/plains -its always irrigation).
draw your own conclusions --but not about the poster.
