We're experiencing situations where 'create task' actions are failing because an SFDC employee/user cannot be found:
Failed: employee with key '[NAME]' not found
This occurs because employee names automatically change whenever they are on vacation.
To avoid this, I would prefer that Marketo used the unique ID (e.g. 005a0000000abcd) when performing the employee look-up, but it doesn't look like it's possible.
Any ideas how to avoid the task creation from failing?
If you add such a field to SFDC, you may be able to do this. But the Task object is a bit harder to handle in this situation.
Perhaps you need a different process to handle Lead Owners who are on vacation.