Based on its gross margin, operating margin, and net margin, FB converts a larger percentage of its revenues to profits than most other companies in the Computer Services industry. Furthermore, the company is profitable with an operating margin of 47.32%.
FB holds a substantial amount of cash and cash equivalents on its balance sheet. These liquid assets can be used to fuel growth, pay dividends and limit financial risk.
It sat next to GOOG and EBAY at different levels of comparison.
One of the reasons that Amazon has such a massive P/E is because they have ENORMOUS revenue (13 billion in the first quarter) and if they can figure out how to get overhead costs down then earnings would be better and this is what investors are counting on. What you describe is a situation where there is no possible way to increase profits by reducing overhead as it is already a lean company. The only way to increase profits would be to find additional lines of revenue. For FB to justify the current price, they're going to have to quintuple their revenue.