I don't like, don't care about, don't want notifications from my window manager. Ever.
Example: Since I manually removed the virtuoso-t package, my computer doesn't spend ages trying to index its own files. I consider that a good thing. When I start KDE, I get a notification that the Nepomuk RDF service cannot work properly without virtuoso. So I have to waste a click closing that window.
I also don't update my packages just because there happen to be new versions of things out. I generally wait a while.
When I use apt-get, which is a lot, I get a notification that there are a number of new 'system updates'.
Every single time.
Like punishment.
I'm not interested in using LXDE or XFCE. I prefer pure KDE in a lot of ways. But if I could suppress all of KDE's messages, more in line with the 'no news is good news' user experience, that would really be superb. I'd have so many fewer windows to close at various intervals, after all.
Best Answer
In KDE 4.8 (sorry I don't have access to anything older ) you can click on the "show hidden icons button" in your panel, then right click on "notifications", click "notification settings". Here you will see some options on what to show. However each application has it's own menu for what events it has send notifications.
An even Better option might be to go to the K menu, click system settings, click desktop search, and disable all of the enable desktop search services. You didn't have to unistall virtuoso, just disable nepomuk via settings.