We reject competitors from coming to our database, however, we have a fair amount of competitors that are marked as "Unqualified" in SFDC. What are some best practices on dealing with competitors that are already in the database?
Should we just keep them in "disqualified" pool?
"Unqualified" in SFDC are still marketable via email in Marketo. I would take a look at the system field "Black Listed" for competitors which prevents any email (marketing or operational) from being sent to them.
Generally you'll see the "Black Listed" field being used for this, or simply setting up Exclusion Lists to ensure you aren't marketing to competitors. I have seen some simply remove competitors from Marketo and keep them in SFDC alone, but this isn't necessarily best practice.