Congratulations?

Well, the news about my promotion has been public for a week now and I have been very interested in the response I have got. The few people who were closely involved in my application were told first and they were very pleased and congratulatory. I then told current and past members of my research group via email (and promised them a meal out to celebrate) and got some nice emails and some shy personal congratulations from the more junior ones. Then when our Head of School made the news properly public by email a few people in our large department sent me short congratulatory emails - these were mostly people I don't know very well but exchange "hellos" with in the coffee room every once in a while. It staggers me that a few people who I work with more routinely, including vast numbers of our lecturing staff have not emailed me or said anything in person, despite having the opportunity. I have always congratulated people in a similar situation.

One potential reason is that our Department is quite large, and more importantly has grown very rapidly over the past 10 years. In fact we have been having discussions recently about whether we need to create subdivisions to stop increasing fragmentation and restore the friendly collegiate nature which our students and postgraduates value. However, opinion is divided as to whether this would indeed help, or just make matters worse. I'd be interested in the experiences of people who work in large research intensive departments where different structures are in place. Do you find your department to be collaborative or a collection of individual researchers? Does creating subdivisions help or hinder?