I've long given up on expecting a reply when I send in a resume. What amazes me is how rude some people are after you've taken the time to interview with them. Like you mentioned, some will not even dignify you with a quick reply to let you know that you didn't get the job. I think some of this behavior comes from the flawed mindset that some people have. They think "important people are too busy for things like simple courtesies, so if I neglect those, it must mean I'm too busy and therefore important".