Full disk encryption or other situations where manual intervention is a hard requirement to get the system fully back online is one situation. Any instance whe

Full disk encryption or other situations where manual intervention is a hard requirement to get the system fully back online is one situation. Any instance where you're running untrusted binaries on your server you'd want to update ASAP and not worry about getting pwned while waiting for scheduled downtime. Before Oracle closed it to new customers, Ksplice was fairly cheap, ~$3-4/mo/server.