I nod all the time - as I never know if I just missed a greeting from a library member <img src="/ubbthreads/images/graemlins/delight.gif" alt="" /> - can't keep faces in mind. BUT! Ask me 20 yrs later about a difficult question I solved by giving me a key-word <img src="/ubbthreads/images/graemlins/stupid.gif" alt="" />
Kiya <nod-cheater>

BTW, we females seem to be lucky, we can nod+smile at complete strange females and the risk of getting punched is very slim <img src="/ubbthreads/images/graemlins/delight.gif" alt="" />