Facebook and my views of it in the context of Privacy and Security are well known. This conversation with one of their (anonymous) employees detailing a few internal processes and tools is actually quite scary.
Now, I don’t know if this is true and how much of this is true; but if I was working for Facebook then all of this is quite logical and makes sense. And, technically all the things talked about is very feasible and not too challenging (of course am over simplifying here).
I do have to admit that the perf and scalability challenges are quite interesting and would love to sink my teeth in it – I guess I need to look at PHP first. :)