Activities include tasks and events. Unfortuately Salesforce will not let us query the OpenActivities and ActivityHistory sObjects. So you are forced to use two tables. One will be tasks and the other will be events.
We also have an issue with task list. It will not show tasks past a deactivated user. So if a deactivated completed a task on April 1, 2013, the task list will stop at that date. Happens on multiple records and object types.