Notes on Lead Ownership
From SmartWiki
If you want everyone to pick from a list of leads and determine which ones they would like to work with, then select All Leads Available to Everyone.
If you want to direct all the leads from a single campaign to a single person, then set their name as the lead owner.
If you want to rotate leads between people, set the lead owner to someone in an administration role, then they can “rotate” each lead in turn to a different person.
Remember, the leads that individuals will see come from all campaigns where, for any reason, they are set as the lead owner.