Sorry, another thing I noticed on my current map. No idea whether bug or strange feature - and please tell me if I should stop to report these little things. I don't want to annoy you guys with strange features you probably know much better than I do.
Anyway, the steel mill has now ordered enough coal to cover it's demand for the next 4 years or so, clogging up the harbour to constant overcrowded status. Monthly demand: 160 tons, amount of coal shipped to the harbour: 7082 tons. Screenshot here: http://i.imgur.com/kJ1b97b.jpg
I have no idea whether the clerks at that steel mill ever stop, but I've noticed other industries stopping to accept deliveries much earlier.