[gruntled]

A PE of 60 is very high. A very rough rule is that the PEG (PE to Growth, where growth is earnings growth in percent) should be about 1.0.

So a PE of 60 means the market is expecting very approximately 60% year on year growth.

[technotony]

That's probably what facebook is growing revenues, so maybe it's rational. this (a little out dated) chart shows that: https://marketrealist.imgix.net/uploads/2014/05/Companies-Ad...