I took a look at my friend's city bike's gears, as his rear gear shift levers felt almost completely "limp". Other (cleanliness and wear) issues aside, one thing that struck me as odd was that when I pulled the derailleur cable by hand, the derailleur moved outwards, i.e. towards the heavier gears. As far as I know, the derailleur moves towards the wheel when the cable is tightened whatever the model (here it was some standard Shimano). He told me he had bought the bike used, but the gears had been working during his time and he hadn't touched them.
How can that kind of "opposite" mechanics be possible?