I'm with Kent Enfield, had to go with the "No" vote because of the way the question was posed.
Also, the "yes" votes seem to presume that everyone has good communication skills and would find teaching an aid to their own technique. I've met some very good aikidokas who were absolutely atrocious teachers and didn't seem comfortable doing it either. Leaving aside the obvious "it's helping them confront their fears of teaching - thus their spirit" lark, I'm unsure how valuable it would be to their own learning of aikido.
I agree having to teach anything helps you learn it, but I don't think it's necessary.