Here is what I think may be a unique problem. We have a B2B2C model. All of our B2B records were loaded in from SFDC and overall, the sync has been great. It's allowed us to do a ton of good work.
But, we also have a web services API that loads in our B2C records. We have done a bunch of work to isolate the fields being used by our B2B records and B2C records - to prevent overlap. Unfortunately, there remain a few fundamental fields like name and email address. What we are finding, is that at times, our web services API is loading in/updating B2C records that have an email address matching one of our B2B records - therefore overwriting some key fields in both Marketo and eventually SFDC. Obviously, this has big problem potential.
Our gut feeling, is that if we could find a (ideally dev-free) way to tell Marketo we don't want that API to update records that have a SFDC ID - this would squash the problem all together.
Anyone have any good ideas?