When you're young, it can be beneficial to specialize in the "here today, gone tomorrow" technologies, because it negates the advantage of all the greybeards and lets you get exposed to levels of responsibility you wouldn't have a prayer of reaching for 10 years otherwise.
I got my first tech job (at 15!) because I'd taught myself Java, which was then brand-new, and a number of local companies needed experience with that and this weird new technology called the WWW. Parlayed that into a bunch of web experience, often as sole developer or team lead. Parlayed that into a job at Google, where I got to learn information retrieval, machine learning, distributed systems, the stuff that actually has a shelf life.
Someone could certainly end up at the same place (skill-wise) by getting a Ph.D and then a job at Google. The thing is, if you take that path, you're also forgoing work experience, income, perspective on how the industry operates, and the opportunity to jump off into different careers if you find you like them better. My first job out of college was writing software for hedge funds, for example; it turns out I hated the financial industry, but if I hadn't, it wouldn't have been too big a leap to get a job at a hedge fund after that.
The trick is to not kid yourself into thinking that the twelfth Javascript framework you learn is still valuable. The first gives you opportunities, the second and third give you perspective. But after that, have a plan B for things you should be learning that you can't get on the web. All that Java Swing stuff I did around 2000? Basically useless. Ditto the PHP in college, and even my Django & Javascript skills are nearing the end of their shelf life. It's the stuff I've done besides that, the stuff I generally don't talk about on Hacker News, that makes me valuable