I'm writing a trigger to update another object's field. I know a trigger can fire on multiple records. My question is if the records are unique? E.g. A trigger is called with 5 records. Does SF guarantee that each of the 5 records are different or could the same record be in the list twice? I want to use a Map and thought to use the object's ID as the key.
The first example [in this link] (http://www.salesforce.com/us/developer/docs/apexcode/Content/apex_triggers_bulk_idioms.htm) implies a record can appear more than once as it uses a set to guarantee uniqueness.