I had one phone screen with two members of the team, followed by a Skype interview w/ one repeat team member & 3 new people. Each interview was an hour in length, we went over my skills and background and agreed that while I was overqualified for the specific role, there was interest on both sides and it seemed to be a great opportunity. The interview seemingly went well and then there was no follow up, despite my attempts to reach out for next steps or feedback.
It's fine if a company is not interested in a candidate - it happens, but it's extremely unprofessional to cease communication and become non-responsive.