The magic thing with characteristic impedance matching is the word 'matching', means whatever you put at the ends of cable must match the characteristic impedance of cable. And you must do this with every line!
Kai,
first: let me say that I wholehardedly agree with the points you raise in your post, BUT for "once in a while circuits", you can make one exception:
If the data lines are set up far enough in advance of the clock, you can get by without terminating them. This, of course, lead to the trap that if you modify the cable in any way, you are screwed.

Nobody is more adamant about termination than the undersigned, but as stated above for "once in a while circuits" with a sufficient setup time you can get by without terminating data if you terminate clk, stb etc.

Erik