Thank you for sharing this!

I was under the impression banks are happy to get 5-10% profit margin these days, is there a distinction between operating margin and profit margin that explains that?

That's not really comparable because banks and insurers require a huge amount of capital to earn those margins. For example, JP Morgan (a pretty well-run and profitable bank) made a ~32% operating margin in fiscal 2015. But JP Morgan's return on tangible equity (a measure of net profitability relative to capital used) was only ~13%. Facebook, on the other hand, had a return on tangible equity of 25% in the last quarter. And as time goes by, that return on tangible equity should increase quite a bit for Facebook, while it is highly unlikely to improve all that much for JP Morgan because of competition in the banking industry.

They have 1.79 billion monthly actives. See any threats on the horizon? I don't. Snapchat for example is more likely to remove a chunk of Twitter's audience than harm Facebook. I can't name a single fast rising Facebook competitor, anywhere in the western world (China obviously has its own social juggernauts).

It's likely to continue to be the only social network in the west that is truly wide, spanning almost everyone. That will probably be worth $40+ billion in ad sales in two or three years.

15 years ago, who thought a search engine could scale to $80 billion in advertising? Essentially nobody. Microsoft at the time had $23 billion in sales. You would have been laughed off the planet if you forecast Google's search engine to be worth so much.