Facebook is valued at over a hundred billion dollar. Yet Facebook revenue does not exceed 4 billion dollars. That is revenue not profit.
And what does Facebook make exactly? And what exactly is its future potential income? Considering the business model, it is hard for me to imagine that Facebook revenue will ever exceed that of Google.
That puts a cap on the profit from the get go. Furthermore, I believe this "marketing" scam is going to die within the next 5 years. Just like in stocks, your "system" works as long as no one else knows about it and it is not big enough to alter the system dynamics from which it was derived.
All the fancy "advertising" is being beaten by lower prices. Remember Circuit city, Best Buy and compare them to Walmart and Target. I do not think CC lacked advertising, but they died and so will Best Buy (unless they find a new business model). The price war will by itself shrink margins and phase out any non-essential production cost. Facebook is a great idea but not a great stock (even according to Zuckerberg himself), at least at the current levels. Never try to be a "me too" investor. You do not want to buy the hype but want to sell it.