The urgency to interview, followed by the abrupt halt in communication isn't something that is unique to Silicon Valley or engineering positions. I had it a lot in London a couple of months ago for mostly product jobs.

It's incredibly unprofessional / downright rude - especially when so much pressure is put on to get you through the interview process quickly. It also means that I now have a negative opinion of a number of companies - and advise friends against applying or interviewing there if approached.

I've been in a position of hiring before, and while it's not nice to tell someone that they haven't got the job, it's the polite thing to do. Most people are reasonable, and it increases the chances of them recommending your company to others.