Although, the Khan Academy process involved many hours of mid-day Skype interviews, phone calls, and a relatively time-consuming take-home assignment followed by a curt thanks-but-no-thanks form letter and an encouragement that I volunteer for them. So ultimately not a success.
To be fair to Khan Academy, they seem to be part of a bigger trend towards increasingly time-consuming interview processes that span weeks or months. Start-up companies are in the enviable position of asking for higher investment from applicants, while not offering a higher return (perhaps the idea is that the possibility of landing the job should be its own reward -- but wouldn't this be mutually beneficial for both the applicant and the company?).
Or perhaps this is the logical extension of a community built on the idea of work-hard-first and (possibly-)get-compensated-later, or "long-term compensation" [0].
Not to say any of this is necessarily wrong or bad. Supply and demand will dictate what the job market can bear, and if a company is receiving a glut of talented applicants, it's their job to thin the herd the best way they know how.
The key is probably knowing your audience. Personally, I gave up after I shot a few e-mails to jobs@ from here and never got a response. I imagine better hackers simply don't have the patience.