To be at 100, FB would need revenue of around 50 billion. That's a little over seven times what they are suppose to earn by the end of the year. At the growth rate they have now of 40%, it would take fb over 5 years to achieve that. 40% is very high earnings.
So if you think 5 years at the end of this year are soon, okay. I think there is a long way between now and then so look at some nearer term targets.