If everyone did this, it wouldn't work. It would just raise the noise level.
That's the beauty if it. Everyone can't do this, because it takes work. It's customized for the specific company, and that's the only reason they work. It's like a cover letter on crack. If he made one that didn't find AirBnb's visual style, that didn't include specific information about what makes him special for AirBnb, it wouldn't succeed.
You've missed the point: The fact that someone did "work" doesn't mean that they're qualified. It just means that they're enthusiastic enough to make a website for a single employer. And that's great, but it's just the start of the whole hiring process. Once you get noticed, you also need to prove that you're a good engineer, employable, a culture fit, etc.
The OP was (vaguely) implying that the success of this guy's effort indicates that everyone else is somehow Doing it Wrong, because we're using jobvite, passing around resumes, etc. But what this guy did is the digital equivalent of those dudes who pay for a billboard on the freeway that says "Hire Me". It's a clever trick that may work for the first few people who try it, but it won't work consistently. The rest of us are still going to need a resume, recommendations, etc.
That's the beauty if it. Everyone can't do this, because it takes work. It's customized for the specific company, and that's the only reason they work. It's like a cover letter on crack. If he made one that didn't find AirBnb's visual style, that didn't include specific information about what makes him special for AirBnb, it wouldn't succeed.
Proof of work. No way to automate that.