Really? Might it be that we purify memetic procreation of its inefficient dependency on support systems engineered for DNA-genetic procreation?
Nothing, really. A voice in a chatbox is still only in a chatbox, and this whole prospect will creep people out sufficiently to make them leave Facebook.
(My mother apparently has something called "Google Cards" on her phone that creeped her out by reading her email and giving her reminders of things. Facebook false-friends that imitate living people without being living people are going to creep her out even more.)
On the other hand, the scientist in me notes that if you're actually trying to make my Facebook False Friend more interesting than a real person, you're going to have to teach it to fluently and accurately discuss research-level science and mathematics, teach me analytic philosophy, and then argue about which anime characters are best. That's really asking quite a lot! I don't think Facebook will accomplish anything quite that "scifi" in the next few years.
You've just interacted with me on some level, but what's to say I exist? Pretend I only have social network profiles online for you to background check. Those would be easy to dynamically and convincingly generate.
And don't just imagine your reaction, but the reaction of multitudes of people who aren't skeptical about religion, about crystal healing, who are superstitious, who watch whatever is put in front of them, etc.
I bet someone could scan my body of online work and design an array of profiles that might pique my interest.
Imagine that they're more attractive, more flattering and more interesting - what happens next?
I can see us becoming like the animal that dry humps some false approximation of its mate, unable to tell that it's stepped away from reality and is just fulfilling its desires without procreation.