A Bug in VMWare ESX 3.5 Update 2 prevented Virtual Machines from booting on 12-Aug as it (the bug) had "expired" the licences used !
"...many corporate users woke up to one of their worst virtualization nightmares: not being able to power on critical virtual machines even though the host server seemed perfectly fine ..."
I get uncomfortable with software that uses licence keys, "registry" settings etc that "expire" or "disable" software in this manner.
The expiry of SSL Certificates can cause some "loss of face". Similarly, the failure to renew domain names (remember Microsoft and passport.com and hotmail.co.uk ?) can be very embarrassing.