1) I want to track domain names that someone else owns, and sort them by expiration date.
2) I want to track domain names that I'm considering buying, and add notes like "Mark and Denise liked this name, so I should probably buy it."
3) I (unfortunately) have my domain names at different registrars.
4) I want a brainstorming tool to help me find available domain names based on keywords. Some programs let you enter keywords and they'll create a list of matching domain names and then check their availability.