My question is, has anyone else seen or done this? All of my peers I have spoken to have advised against it, and my initial reaction was in line with that too.
You and your peers are correct. It's a disaster, and a disaster that isn't so much waiting to happen as inherent to the approach.
If we force a duplicate, is there any way to tell Marketo to always put the latest activity to the newest lead, my understanding is it will attach activity to whichever its algorithm finds first.
"Its algorithm" is too general. The way Marketo looks people up depends on the activity, but it's never random. And it almost never chooses the most recently created lead. For example, form fills find the most recently updated lead (regardless of update source). Email clicks are logged to the lead ID that received an email. Web activities, once a Munchkin session is associated with a person and isn't reassociated, continue to be logged to that person.
If we create duplicates how can we make sure to avoid any sync errors for having duplicates in Marketo?
What do you mean by sync errors? 2 different Marketo records can be synced to 2 different SFDC leads (and/or SFDC contacts). There will not be errors during sync because the relationships are between SFDC IDs and Marketo IDs (not email addresses). However, I would argue the entire setup represents an error state, because actions related to the same human are being spread all over the ecosystem.
- Are there any other risks to proceeding this way or on the other side benefits to this that I am not thinking of?
There are no benefits to this approach over properly managed Opportunities.
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