Well, it is not the iPhone itself that can sync Palm memos. It is rather a feature of Notebooks that allows you to import memos you have exported through Palm Desktop.
Exporting the memos from your Palm actually should not create any copies, because the process basically is like this:
1. export the memos in "tab delimited format" from Palm Desktop
2. apply a few conversions on that file if necessary
3. change the file extension to .palm
4. import into Notebooks
The handbook is available for download here: http://www.notebooksapp.com/Download.html
I hope this helps.