Too many times I've been invited to wish a deceased friend "happy birthday." I go to their page and find it memorialized. Nevertheless, there are many friends wishing them happy birthday, oblivious to the indication that the page has been memorialized.
The worse was the time my wife discovered her brother had died via FB. He had estranged himself from the family decades earlier, but still... A shared friend posted the status to his page, otherwise we might never have found out.