Given that the memo was created on MS Word, my guess is that it's not the latter. If you can use a computer, you probably have some grasp of the internet.
In my view, the creator was, as you say, too young to be familiar with typewriters. But the contractor, i.e., the person he/she handed it to, was the one who was too old to understand the power of the internet.
Based on USA Today's description of their source ("familiar with the workings of the Texas NG, worried about retaliation", etc.), Bill Burkett is the logical candidate. And Marianne Carr Knox fingered him, as well.
I've no doubt that Burkett is involved and, perhaps, was even part of the chain-of-custody. But I don't see Burkett either a.) creating the documents or b.) handing them over to Dan Rather...and thus serving as his "unimpeachable source".
At this point, I would suggest that the chain-of-custody would look something like:
creator-unknown hands (inc. Bill Burkett)-DNC-Kerry campaign-unknown hands-unimpeachable source-Mary Mapes-Gunga Dan.
That look right to you?
Perhaps a listing in the News/Activism sidebar...???
I agree 100%