When your professional contacts outlive their use

In this age of communities, new-web contact lists, and instant messaging replacing the Rolodex, how does one not only "trim" their contacts... but also deal with the reactions.

In a recent posting, Chris Brogan discusses trimming down his facebook friends list, and his need to do a little cleanup on his extensive followers. Something I'm sure everyone does from time to time.
Now, I'd like to go one step further...

I wholeheartedly agree with Chris' point that these "friendships" and "followers" are simply data (don't get me wrong, Chris is not de-humanizing), but when you're working on a smaller scale like myself or many others, there may be some actual repercussions.
In the old days (haha yes I said old days) one could simply just remove a name from the Rolodex or toss out a business card and that was that. Currently though, when you remove a person from your "X" list, they know about it. So, how do you deal?

I've personally been put in a situation that makes it obvious that one of my useful contacts is no longer useful, both professionally and personally. Now I am faced with the issue of how to deal with this situation without making myself the bad guy and without affecting other relations.

Chris often talks about "building an army," but how does a dishonorable discharge affect the end goal?