When deciding whether to give an employee a raise, sometimes it's not so obvious. If an employee is doing a fine job but not an outstanding job, it's easy to put off giving them a raise until their performance improves. However, there are some employees that are so important, that go so above and beyond what anyone else could do that it would be a foolish error not to give them a significant raise. After all, if you don't give them a raise, they can easily pack up their bags and find a different job that pays them more, especially in this economy.
One Reddit thread tells the story of this exact type of employee. He's essential to the running of this company, but the HR department refused to give him the raise he deserved. He left the company for a better opportunity, and that has set the company on a path that might lead to its complete and utter destruction.