It would be helpful if an issues owner or assignee could enter an email address to be added to the watch list for an issue. An example use case is:

1. Help desk receives an issue from joe@blow.com.
2. Help desk enters the issue into JIRA on behalf of Joe Blow.
3. joe@blow.com is added to the issue's watch list, preferably during issue creation.
4. Joe receives an email regarding the creation of his new issue.
5. Any modifications to the issue are also emailed to Joe.

It would be more convenient if Joe did not have to be a "registered" user in the system.