Elyse Vahjen(c)
In Account > Account Settings > Recent Activity
http://www.geni.com/account_settings/recent_activity
there is a setting for
Online Collaborators
untick the box for "Include my collaborators in the Recently Online module on the Home tab"
You should also notice the "Filter ▾" option to the right of the Recent Activity column on http://www.geni.com/home