I am not going to defend MS security (or lack), but I just don't see rebooting happening around me or with any of my machines. I constants run 40 to 45 services - Homesite, Dreamweaver, Outlook, Access, 3 or more instances of IE and often Enterprise Manager at the same time. I am running with 640 MB of RAM and Windows 2000.
In my old office the only people rebooting were using ME or 98. It just did not happen.
I shut my computer down on Fridays... just to be safe.