This was generated as a suggestion on support issue: https://support.atlassian.com/browse/JSP-74071

While following the advice in:

http://confluence.atlassian.com/display/JIRA/How+do+I+assign+issues+to+multiple+users

Everything looks fine but I would like to be able to set that group field to a default value and hide it so the reporter doesn't have to fill it each time.

From the mentioned report it turned out that such fnctionality is not available.