As a hiring manager in a large company, I can tell you that most of the people you are interviewing with aren't being actively rude, they are overwhelmed.

If I took the time to contact all the people I passed on to give them an explanation, it would consume more time than I can afford. The people making the decision to hire are - usually - the ones with the most to do.

The safest bet is to consider any lack of communication a "no." Personally, if I want to hire someone, I make the offer on the same day I interview them. Any company worth your time should do the same.

On a side note, you should make a habit of giving and getting business cards from your interviewers - particularly the decision maker. Also, turn the interview around if you can. Your talents are worth a good company. Make THEM SELL YOU on their job. Don't take a stance of hope. Make sure they leave the interview knowing you are the right person, and the question is "will YOU accept their offer?"

Good luck!