I usually treat most forms of social media a lot like i treat the huge spider that lives in the corner of my yard, I try to ignore it and hope it goes away, but this was way to wierd to ignore. A service called LivesOn promises to use software artificial intelligence to learn your Twitter feed habits, likes and dislikes, etc. and issue new Tweets for you... after your dead! I don't do Twitter but if I did and I got a Tweet from someone I know is already dead I'd unfriend them, abandon the account, and seek professional help.
(and if you'd be interested in this creepy-assed service; no offence guys; I suggest you save us all the hassle of hearing about your all-consuming love of Justin Bieber and Team Edward and just get a life now, while you still can...)