FB has had solid revenue and net income for many years, so much that it’s one of the most valuable companies in the world. It’s not comparable to MySpace, and definitely isn’t going anywhere anytime soon.
While Facebook and MySpace are different in many ways, the average lifespan of a S&P 500 company is below 20 years.
Facebook could very well be an outlier. If it isn't, it could definitely go away in the coming years.
In any case, that shows that its revenue/income is not a predictor of anything. When a company spirals down, it does so at an accelerating rate and can quickly burn through any amount of cash.
Facebook is very far from an average SP500 company, as are the rest of the big tech companies. They drive the market indices with how much investors think they are worth and will be worth. And they have levels of cash that tech (or any) companies in decades past could only dream of.
