On German motorways there is no general speed limit for cars. For lorries and any other vehicles exceeding a weight of 3.5 tons, there is. This creates a problem in that it 'forces' every driver to leave the right lane for the use of trucks only - disregarding the simple fact that the law requires you to drive on the right lane when you're not overtaking.

The left lane, on the other hand, is strictly reserved for two kinds of people:

Drivers of Mercedes, BMWs (preferably dark coloured). When you're driving a really fast car which happens to be another brand you can just about get away with using this lane if it's dark blue. If it's white, forget it.
Nice, balanced, well meaning drivers who want to introduce a speed limit (of about 100-120 km/h) or simply detest speeding. They usually indicate right when they see somebody approaching fast in the rear view mirror - and switch the indicator off when the other car is nearly on their trunk (without changing lanes, naturally). Of course, this is done purely as an educational measure. Incidentally, they never dare 'educating' when the approaching car is a dark Mercedes or BMW.
The real trouble starts when there are only two lanes, which usually leads to frenetic honking, repeated headlight-flashing and indicating on the left lane, while the right lane lies deserted apart from the odd lonely lorry every now and then.

When you try to overtake somebody on the right lane, be careful not to exceed their speed by more than 5 mph. When in a traffic jam, always change to the lane which goes fastest. Every inch counts, and it's not your fault that everybody tries to do the same. When there's no movement on any lane, use the hard shoulder, that's what it's there for (apart from undertaking).