Am I being ignored after an interview? I have had multiple situations (ok, well only two) where after what I thought to be a positive Skype postdoc interview (in one case, two interviews), my follow-up questions/requests have been completely ignored. I've sent 2-3 follow-up emails spaced over weeks with nothing in reply. In one case it's been over a month. The weird thing is that the email exchanges prior to the interview(s) to set a date/time happened very quickly and were enthusiastic. I thought the interviews went well and they said certain phrases like "you seem to have very relevant skills and interests." I made sure to thank them in follow-up emails and I asked a few more logistical questions about their group that time did not permit in the interview. But nothing in reply.

Maybe they decided they didn't want to hire me. That's fine, I get it. But I'm very frustrated with this because its seems to be so unprofessional. If they don't want to hire me, why not give me the courtesy of saying no so that I can move on? The field is not that big, so it is very discouraging that I would now have two groups that I need to avoid. 

My question is if this is typical for a group leader to just ignore emails like this if they don't intend on hiring an applicant? Or is it possible that they suddenly became very busy and aren't able to answer emails?
Well, I had quite a few postdoc interviews and I can tell you that it is NORMAL for a PI not answer you back. Of course it is a shitty situation, even more when you thought the interview was good, but that's how life is when you are searching for postdoc positions.
1 email as a follow up or an update is ok. But don't insist on it. The truth is: you know as soon as you finish the interview if you would hire the applicant or not, so if you don't hear from them after a week consider it a no.