Harrybarry 0 Newbie Poster

Hey all,
I’ve got a question about Facebook. I’ve read in an article that Facebook could also be written with C++ and would work more efficient than what’s currently happening. I’ve heard of numbers with 75% reduction in for example servers. I would like to ask the experts here for their opinion.
What are the parts you -can or should- write in C++ instead of PHP looking at Facebook. Or can you completely create their service with C++?
Is it true that the systems will run much better/efficient when there is more C++ in Facebooks service?

What are the downsides when you develop a web service in C++?
Hope my question didn’t irritated you too much and thanks in advance for your time!