In theory the reason for this is that Facebook is "stickier" than Google or Amazon. If Google search isn't working for you, you can switch to something else in a heartbeat. If Facebook isn't working for you, you have to get all your friends to switch to something else before you can.

The problem is this is also going to be Facebook's downfall at some indeterminate future date. Because if some other social network ever becomes more popular than Facebook, Facebook is over.

In fact it can last. Your information is wrong.

Amazon has a radically higher multiple than Facebook. About six times higher, being charitable with Amazon's flaky net income.

Facebook will hit $13 or $14 billion in net income for fiscal 2017. Explain to me how a 27 or 28 pe ratio is unsupportable when you're growing net income at 30% or higher.

Meanwhile Google is growing its net income at 18% with a PE of 30. A far more lopsided ratio than Facebook has now, and one that is going to get much worse in just the next four quarters.

So you're wrong on both counts. Facebook has the superior value proposition based on valuation to net income + factoring growth rate.

I used to think this was dumb as well, until I realized that if you type "google" into the address bar of Chrome, Firefox, or Safari (possibly IE too, I haven't used it since IE6), it runs a Google search. Nobody ever bothers with the .com anymore; why should they, when just typing the name of the site in will get to it? So a sizable number of people who go to Google Search get there by running a Google Search.

Also, a surprisingly large fraction of users cannot touch-type. They've been trained to go to Google to search, so they type in g-o-o-g-l-e-ENTER and get where they intended, and never notice the autocomplete suggestions showing up in the Omnibox or the fact that they could just type their whole query in and get answers.