>> tl;dr if it'll take the company more effort to reply to your email than you put into sending it, you're doing it wrong.
from my side of the table, when I was interviewing (about 6 months ago), probably 8 out of 10 startups that I applied to and interviewed for didn't bother to contact me again - not even a polite "thanks but no thanks". I'm not arrogant enough to think I'm the perfect fit for every company I apply to or even that I aced every interview, but I would think common decency dictates at least a response or acknowledgement after an in person interview.
from my side of the table, when I was interviewing (about 6 months ago), probably 8 out of 10 startups that I applied to and interviewed for didn't bother to contact me again - not even a polite "thanks but no thanks". I'm not arrogant enough to think I'm the perfect fit for every company I apply to or even that I aced every interview, but I would think common decency dictates at least a response or acknowledgement after an in person interview.
Two sides of the same coin, in my opinion.