Back to the Future - an awesome movie. Also, an appropriate lead in to todays discussion. You may think feedback is looking backwards, but it is really looking to the future.
Feedback uses a past event as an example, but the entire focus is on the future behavior. If the employee did something well, you want them to do it again. If the employee could do something better, then give them the direction to improve.
It's why when I give feedback, the conclusion becomes critical. For positive feedback, I say something like "keep it up". For negative feedback, I either tell them a specific thing to do or I ask "what can you do better next time"? I don't want the employee to focus on the past behavior that was the example - they can't change that - I want them to focus on the next time. I want them to think "the next time I am in that situation, I will do X", not "I shouldn't do Y".
This really comes into play with negative feedback - because it takes all the emotion out of it - or at least some of the emotion. If managers give feedback when angry or upset, they won't focus on the future. It requires that the manager not give feedback when emotional. It is really hard to be forward thinking when you are emotional about the past.
Think about the last few times you gave feedback, did you focus on the future or the past?