Hi Dan,
We spent a lot of effort getting rid of hundreds of duplicates that were in both Dynamics and Marketo when we started with Marketo, but now have it under control, although we have to monitor constantly. And some problems have remained persistent. (Old duplicates that are Inactive still interfere with sync.) We have emphasized with sales that they should look for duplicates before creating any new records.
If one is at the point of not allowing Sales to create new leads, what about the option of a customized Marketo form for Sales to enter the new leads? I haven't set this up, and can certainly think of some cons, but it could cut down on duplicates since Marketo sees the info first.
Best, Shannon
You bring up one of our key pain points that we've been experiencing - and that's "inactive" leads in CRM remaining visible to Marketo. We never delete in real-time - instead, when a lead is disqualified or qualified (contact created; or merged into existing contact), that lead is deactivated. Once Marketo records the status, it should never have access to those inactive leads again. We have a working session next week to figure out ways around this.
I'd also be interested in the strategy/tactics you used to get both of your environments under control.