Dreamforce presenters need to be able to edit their presentation details (summary, presenter biographies, etc)...

The Presenters junction object expresses a dynamic user-to-record relationship: each Presentation has a different set of users who must be able to edit it, and that set can change over time. Apex-managed sharing is appropriate because a trigger on the junction object can create a share when a presenter is added and remove that access when the relationship is deleted or changed. The Presentation object ' s OWD can remain Private while only the users represented by the junction records receive the necessary Edit access. A permission set cannot grant access to one specific Presentation record; it supplies object, field, or system permissions and must be combined with a record-level sharing mechanism. Standard Sales Team functionality also does not apply to an arbitrary Presentation custom object. For a robust custom-object design, the implementation should use a dedicated Apex Sharing Reason so the programmatic shares are easy to distinguish and manage throughout the record lifecycle. Study Guide reference: Access to Records - Apex-managed sharing, junction objects, dynamic user-to-record relationships, custom sharing reasons, and Private OWD.