Facebook is doing an admirable job replacing rotting pieces of their infrastructure with more robust replacements. HHVM replaced the execution environment for

Facebook is doing an admirable job replacing rotting pieces of their infrastructure with more robust replacements. HHVM replaced the execution environment for their code with a more robust code generation/ runtime system. Hack allows them to bootstrap their code base into higher degrees of reliability without a mass rewrite. Also Brian O'Sullivan is one of the best people on the face of the earth to be trying to find practical ways on integrating PL research into practical engineering.