Comment Node.js (Score 2) 453
So... Node.js, chalked full of easy ways to leak memory (ie don't change default debug console, or use a crappy gzip library) but the ability to write code that runs/renders either on the server or on the client with the same code and low-level libraries to make the decision of the best place to render--ie render same code on server or client--makes JS on the server-side rather attractive. I run, Operations side, over 1000+ websites on a Node.js farm (talking 200-300 mbit/sec of sustained daily web-traffic), and it scales a lot better than PHP from both a templating side (many similar but different sites with inheritance based properties) and from the performance scaling side.
From a PLT side, yea, JS ain't the best, but it's a defacto web-rendering technology and its use on the server can simplify a lot of things, not to mention that JS in V8 is pretty quick to boot, although it does have heap limitation based around the 32-bit code V8 generates.
I leave comment readers with a wonderful link: This PLT Life