Most marketing automation systems and CRMs build your database so each contact/prospect/person has a primary key that is the one way that they should not be duplicated in the system. Some are more advanced, but, for the sake of this blog post, I am going to generalize. If you wanna talk specifics, about your database and what to do about the fact it never seems clean, call me, we can figure it out. I digress, and it's only the first paragraph... So, you have this one key and yet, you end up with duplicates. How is this possible and how can we get it to stop?
Where do my duplicate leads come from?
Humans; we are such a finicky breed. And we like to be unique and different and hope that we're still smarter than the computers. But, other humans, who know your tricks, built the computers and the systems. So, when people come into your system sometimes they might use a different email address than the last time they were there, or they spelled their last name differently, or they said they were from a neighboring state, not their own. My very favorite is when they use an abbreviated version of their company name. Depending on the system you have any or all of these things can create duplicates. If people clear their cache on a regular basis, then your nifty system that used to be able to tell when they would come back to the site suddenly thinks they are a new person, throwing everything off.
How can I clean my duplicates without manual intervention?
If you are using Salesforce, I HIGHLY Recommend DemandTools by CRMFusion. It's not the prettiest UI, but it’s like a catholic school nun when it comes to reading the mind of your database. It makes connections and associations I wouldn't have even thought of. Someone typed in ABC Corp as his or her companies name the first time and then ABC Corporate the second time. It finds those and says "well, looky there, we have a Richard Smith in Virginia at both of these companies, I bet it's the same one. MERGE!" It's awesome. And the best thing about it is that you have control, and you can check every single leads before they are merged. You can build the rules the way you want. Or, if you have been at this a while, you will learn that you built such great rules, that you can just merge with little to no digging.
Marketo has a "possible duplicates" report that it automatically says "we think this Richard Smith, is pretty similar to this other Richard Smith, can you verify that for us?" Now, I appreciate them putting it into a handy list for me, but then I have to manually merge each pair, which as you can imagine, can take some time. But, it's worth it. As I said, good data... it's your lifeblood.
I haven't seen inside Silverpop or Eloqua in a while, I would assume these each have similar features.
If you don't have Salesforce, or DemandTools, or a marketing automation system, get an intern with a brain, and patience, and get them an excel spreadsheet. And, after 3 months of that work, give them a real marketing job, because goodness knows if they spent 3 months cleaning your data, they get how important it is, and what a pain dirty data can be, and they will be your data dictator forever.