Do you want someone to post online for you after you die? Do you want to leave enough info behind so a machine can do it for you? Do you really care? Does anyone care what your responses or interests are once you are dead? I think this concept panders to those who believe they are the center of the universe. Some people do care and want to express themselves on earth after they leave it. Really bossy, controlling people would love this idea. They would eternally get to express the last word much to the dismay of their families.
There is a new site called Eter9 which will respond for you after you die. You provide a profile and select preferences. There was a prior system called Virtual Eternity in 2010, but it ceased after 2 years. Still, 10,000 people signed up for it. I wonder how many of them died in that 2 year span and got anything out of the system. FB and MIT are both working on means to improve artificial intelligence to be "better than humans" or to continue for you somehow after you die. Currently, FB allows a specified person to manage your account after you die. How much space will eventually be occupied by the dead? It will just be dead air....Ha ha. Read more about it here http://www.bbc.co.uk/newsbeat/article/34015307/eter9-social-network-learns-your-personality-so-it-can-post-as-you-when-youre-dead