>> My 2 cents: a typical case where this could be useful is:
>>
>> switch (foobar) {
>> case long_enum_value_name_a: printf ("a"); break;
>> case long_enum_value_name_b: printf ("b"); break;
>> case long_enum_value_name_c: printf ("c"); break;
>> case long_enum_value_name_d: printf ("d"); break;
>> case long_enum_value_name_e: printf ("e"); break;
>> case long_enum_value_name_f: printf ("f"); break;
>> case long_enum_value_name_g: printf ("g"); break;
>> case long_enum_value_name_h: printf ("h"); break;
>> case long_enum_value_name_i: printf ("i"); break;
>> default: printf ("?"); break;
>> }
>
> Here's how I'd type this:
>
>  case long_enum_value_name_a: printf ("a"); break;
>  c M-/ DEL b : p M-/ ("b"); b M-/
>  c M-/ DEL c : p M-/ ("c"); b M-/
>  c M-/ M-/ DEL d : p M-/ ("d"); b M-/
>
> etc.  (And if the series are indeed longer than a couple of lines, a 
> rare case indeed, then a keyboard macro is in order.)
>

Yes, that's one way to do it, perhaps the most "emacsish" way to do it. 
But it takes more keystrokes than what you write:

case long_enum_value_name_a: printf ("a"); break; RET
c M-/ SPC l M-/ DEL DEL b : SPC p M-/ SPC ("b"); b M-/ ; RET
c M-/ SPC l M-/ DEL DEL c : SPC p M-/ SPC ("c"); b M-/ ; RET
...

And yes, keyboard macros can also be used.

That doesn't mean that the proposed feature wouldn't be useful; I'd say 
it's more intuitive:

case long_enum_value_name_a: printf ("a"); break; RET
C-u 8 C-x r z
C-s a : RET
C-b C-b C-d b
C-n C-b C-d c
C-n C-b C-d d
...