Best Practice for Setting Default Person Last Name & Company Name

I'd love to hear some suggestions (or cautionary tales) on how to you have used the Default Person Last Name and Default Person Company Name as part of the SFDC Sync Options.  Obviously, the better option is to have a data-append tool to update this info (which we're working on), but short-term want to make sure everyone who is engaging is being sent to SFDC for follow-up.

Set Default Person Last Name and Company Name - Marketo Docs - Product Docs