Always because some of the people on my circles don't really care for the things I say work-related. But then I thought I'm only showing my work-related stuff to a circle of coders and the whole world is missing it.
I believe I wanted Google+ to fix this problem for me, I was expecting a place where I could do my private life (with circles) and improve my professional life (public but without annoying some cirles of the private life).
In the end, I just feel lost not knowing how to use that pretty thing...