Richard Millington draws inspiration from BJ Fogg, and looks for the trigger to make new members stick.
Existing, established, members visit the community several times per day out of habit. For new communities (and new members) a trigger is required. How will visiting the community become part of the daily routine.
Of course, if the online community was a mailing list, then the message is the trigger.
See original article at Your Community Needs A BJ Fogg Trigger