The programming world has been abuzz about the JVM and all these new JVM languages the past few years. I'm a long time rubyist and a lisp weenie, and two of the most popular alternative JVM languages are JRuby and Clojure (a lisp). They are both great langauges, I've done large projects in both, and I really want to love them. But I can't, and it's not their fault, it's the JVM.
Put simply, it's the memory stupid. Have you ever spun up a 'hello world' web app on the JVM. Doesn't matter if it's Java, JRuby, Clojure, or whatever; it will use over 100MB of memory. That's a shit load of memory for a 'hello world' app. Spin up a rails app and it's over 300MB! I know a lot of you are thinking that this isn't that much in the larger scheme of things, that programmers are expensive and memory is cheap, but that's missing the point. I'm a programmer because I love programming. I particularly love making websites and apps for whatever crazy idea I have in my head.
I have a cheap VPS with about 1 gig of ram, and I use it for numerous little websites. Yakkstr, this site you're on now, is one of them. The yakkstr setup is fairly standard, a web app, background workers, and a full-text seach engine. I'm using less than 100MB for all of them combined. The same setup, using the JVM for each, would be well over 1000MB, 1GB, an order of magnitude more memory!
I can't run my hobby sites on the JVM, it would cost me 10 times as much because of the amount of RAM required. My ESP says many of you aren't convinced that my hobby projects matter in the "real world". Let me say this, the history of the tech world should be a reminder that disruptive technologies are usually bottom up. Linux, MySql, PHP, Ruby, etc, etc. It's the hobbiest, the person who writes code for the love of writing code, that disrupts the tech world. And for hobbyists who do web dev, the JVM isn't an option. In the end I'll bet this matters for more than just my hobby projects. The JVM has lost my mindshare, and I'm sure there are many more passionate programmers who are in the same boat.
Which is why the rest of the world uses PHP for their webapps... Ow sucky language you say? True.. but it got a low memory footprint and high performance, choose your pig.