Version:            (using KDE 4.4.0)
OS:                Linux
Installed from:    Ubuntu Packages

 I'm running SC 4.4.0 from the kubuntu ppa repository on a freshly installed kubuntu 9.10. I run the netbook form factor/workspace, which shows the plasma activity in the window list (shows up when I Alt-Tab). I don't know whether this is a bug or a feature, it's actually quite handy, so it could be a feature :-)

 Now for the bug: when I focus upon plasma-netbook either by selecting it in Alt-Tab or by clicking the activity bar in the top panel, I can actually close plasma-netbook by hitting Alt-F4. Checked it with top, before plasma-netbook is there, afterwards it's gone. Running plasma-netbook in krunner?(the Alt-F2 thingy) brings plasma back again. 
 
 This happens no matter which activity is in focus, the SAL, the Newspapers, or the Desktop activity I was messing with (and which is pretty much non-functional in the netbook workspace/form factor, see bug 228286), so it's independent of the type of activity. 

 Bug 227269 also mentions plasma-netbook appearing in the window list, although only when desktop effects are turned off. For me this is always the case, no matter what state desktop effects are in.