How do they make money again?

It's almost like they're running PHP.

I would really like to rag on them for this, but the only problem that PHP is causing them is probably filtering out the incompetent n00bs that want to work there (and the opposite effect -- what hacker would want a PHP job?)

Back when they leaked their code, it was very well written. The frontend stuff was very nice "Hello, <?php echo $username ?>", not "<?php $query = "SELECT * from ..." ... ?>".

Finally, PHP is only slightly slower than Python and Perl, and slightly faster than Ruby.

So although using PHP is a horrible idea, Facebook seems to be dealing with it. It sure isn't the path of least resistance, though. It's much easier to write good $ANYTHING_ELSE than good PHP.

I wonder how much electricity Facebook uses, in total, for all of these servers.

Probably several megawatts. For comparison, the first Russian nuclear reactor, the Obninsk Nuclear Power Plant, produced 5MW.

I estimate about 2 MW.That's only the same power as two and a half Bugatti Veyrons. Or maybe a dozen mortal cars. Or the power of the sun hitting 2,000 square metres of the Earth's surface on a sunny day.

So, not all _that_ much, really.