To clarify a bit further, and to answer KingsRings' question, facebook will accept a request from anyone who fills out the form. The form has a dropdown to select your relationship to the deceased, but friend is one of the options. Anyone who can prove, with a link to an online obituary, that someone is deceased, can request a page be memorialized. (I recently went through the process with a very dear friend's page.)
All of that said, I think it would be rude for anyone but a close friend or family member to submit the request. Perhaps, if someone is bothered by the notifications, the best thing to do might be to forward the facebook protocol to a close family member who can decide whether memorializing the page is appropriate.