Think about everyone who doesn't see this post. Will they figure this gesture out? Did you? If it takes a blog post at the top of Hacker News for people here to find this, it's pretty far from discoverable. Is it really that great if most people can't use it?
On the other hand, you don't need any instruction for pinch-to-zoom. Intuitive interactions like that — or even double-tap-to-zoom — are much harder to come up with, but they're also accessible to everybody. This is a cool piece of trivia, but it's far from solving the one-handed zooming problem. I hope Google (or anybody else) is working on something to make this better for everyone.
On the other hand, you don't need any instruction for pinch-to-zoom. Intuitive interactions like that — or even double-tap-to-zoom — are much harder to come up with, but they're also accessible to everybody. This is a cool piece of trivia, but it's far from solving the one-handed zooming problem. I hope Google (or anybody else) is working on something to make this better for everyone.