Thanks for the answers.
We finally decided to install Cloudingo. Looked at a number of solutions including the SFDC native solution. So far it appears to be working as intended. Although there are still ways duplicates are created and in some cased intentional. Would recommend Cloudingo as the support was excellent when setting it up the first time. We also installed DupeCatcher from the same vendor which is free.
We're currently considering Cloudingo - did you do a mass de-dupe? Did this process cause any scoring issues or attribution woes?
generally speaking list imports, especially from trade shows are the Typhoid Mary of bad data.
Duplicates, nonstandard data (Dear GREGG). list imports are a nightmare.
Cloudingo is a good choice for batch deduping, good tool, great team, but Dupecatcher thier free native dupe preventer will not work well for preventing dupes from Marketo.
Free software is usually more like a free puppy than free beer. If it works, it will take a lot of work to enjoy it.
Prevention is the best practice because whatever it costs to get the data right at the point of creation, it will cost 10x, at least to fix it later.
Don't do that.
RingLead specializes in Marketo duplicate prevention.
DupeAlerts the new-ish native Salesforce app alerts users who enter records in Salesforce that the record already exists, but only after they complete the form and click "save". Ever spend 90 seconds creating a new Lead only to find out that the record you just entered was already in Salesforce? Wow, that is frustrating.
If you would like to share your requirements with me, I can give you some excellent advice.