[nikhilkalegregg]

I think they have enough users that they don't have to worry too much about a replacement. Instagram is pretty close conceptually to Facebook, but most people don't use it as a direct substitute. One thing way in the future I could see hurting them is when my generation --the first generation of users that used Facebook regularly start dying. If I'm an old man and I'm on Facebook seeing daily updates on people I used to know dying, I will probably stop using Facebook altogether to avoid terminal depression, but might just be me. However, if they can keep on-boarding the younger generations, they could probably survive that, assuming their isn't a hipper substitute by then offering users immortality.