you may get lucky being able to get the data from some log, but you need to prepare for the future. No matter what the specs say, it is a good idea to add some extra info and logging.
In really important tables, I have a history table with every version of the row, including LastChgID and LastChgDate.
In important tables I have CreateID, CreateDate, LastChgID, LastChgDate
In all other tables (other than codes tables) I have LastChgID, LastChgDate
when you design the system, you'll have an idea of what is important.
Many of this is displayed on the screen, but even if it isn't, some upset person will call/email who do this? and you can say "you did an 2009-06-02 10:06:22.213!"