I actually knew a guy who died this way at a Caterpillar factory near Peoria, IL. Machine wasn't properly tagged out/locked out.

RIP Troy Bryner

Update:

Per OSHA Report:

Investigation Nr: 200272276 Event: 04/17/2011 Employee Is Killed When Struck By Closing Lid At approximately 11:00 a.m. on April 17, 2011, Employee #1 performing maintenance on a Dunker quench hardening machine that included the repair of a hydraulic leak. He was working in an area that measured approximately 2 feet wide by 3 foot long by 4 feet deep. Employee #1 locked out the machine's control panel and made the necessary repairs. After completing the repair work, Employee #1 instructed a coworker to remove the locks in order to verify that there were no leaks. While in the machine, Employee #1 attempted to lower the machines hydraulic cylinder by depressing the "lower press elevator" button. Instead, he depressed the "lower press lid" button. This caused the machines lid to close on Employee #1's head, killing him. The accident investigation reported that the coworker was working to secure the "lower press lid" cover by chaining it open; however, was not able to secure it in time due to the untimely depression of its activation button.

So, not exactly a failure to lock/out, but certainly an example of how important it is to take those types of procedures seriously. Always, good to know what actually happened.