A very large client with close to 100K desktops and 50K laptops in national offices and headquarters. All machines are keyed with a thumb drive for each employee. Their units will not start without one but the advantage is that any employee with a key can use any other unit. Service people have their own diagnostic keys and the IT people have more extensive keys and no software resides with the user. This was all thought out when a cleaning lady used a labs desktop to download some videos and gamble. She was pretty sharp to have gotten past the site blocker and infested the machine with a rootkit that almost took over their lab network. Now, it is up to each individual to guard his key. This prevents any intrusion attempts from within. Blocking web sites only goes so far and site hijacks are pretty common. Internal attacks from outside can be difficult if you can't get past the firewall.