SV needs to continually reinvent itself, so that VCs can sell their smelly IPOs on Wall St. They needed a new paradigm, so we got Web 2.0. Enter PHP. What is PHP? It's pretty much Perl. In fact, it is Perl. Just a highly shit version, done by monkeys that don't have a clue. Perl 2.0. Facebook, the shining star of Web 2.0, is built on it.
But Web 2.0 isn't new, either. The story of Web 2.0 is how advertising prevailed over technology. Now we're entering a mobile post-web period, where we go back to proprietary lock-in with a cloud twist. It's the 1980s again. But it's fresh on Wall St. Better start learning Objective C. If you believe Android will remain relevant (I personally do not) then keep those Java skills dusted off.