General debug/kernel question

Salve,

I always thought that building a kernel with debug symbols would increase the 
kernel size dramatically. But if I understand things right the additioal 
"symbols" (code snippets?) are not in the kernel but in a different file 
which makes the kernel the same size like without debug=-g. Is there any 
reason to not build it with debug=-g?
Also I thought debug kernels suffer from reduced performance. I also have DDB 
in my kernel and don't _feel_ any difference. So again, is there any reason 
not to put DDB into the kernel?

Thanks,

-Harry