Also suggested during the first Gitify BoF during DebConf13:
git annex drop deletes immediately. In some situations a mechanism to tell git-annex "I would like to hold onto this data if possible, but if you need the space, please delete it" could be nice.
An obvious question would be how to do cleanups. With the assistant, that's easy. On CLI, at the very least
git annex fsck should list, and optionally delete, that data.