Joshua Porter posts a good reminder about how important even the smallest copy can be:

Microcopy is small yet powerful copy. It’s fast, light, and deadly. It’s a short sentence, a phrase, a few words. A single word. It’s the small copy that has the biggest impact. Don’t judge it on its size…judge it on its effectiveness.

It’s also some of the most fun copy to write, especially if your product has a really strong voice.