Is your issue with someone registering multiple people that their cookie is getting updated to point to the last lead record that they registered?
We rarely encounter this situation with event registrations because we use EventBrite and its registration interface provides for entering multiple registrations. However, we do have people submit progressive profiling forms using a different email address and the result of that is we don't capture data that would have been on the first form. In this case, we create a smart list with all of the lead records from that IP address and we can generally figure out which company the submission came from.
We are using dynamic content with segmentations to block the display of content when we detect that a known lead has previously visited or submitted the form from the page. If they are blocked, we do display an explanatory message indicating that they have already viewed the page or registered and to contact their account rep if they need to do it again.
Andy, you can disable pre-fill and remove the munchkin from the page. That way, multiple submissions by the same person will be saved as separate records as long as the email addresses are different.
What happens if the person doesn't pay attention to using a different email address and they use the same one, over and over again, irrespective of other fields? Unfortunately happens all the time.
Landing pages can either deduplicate or not. It's virtually impossible for Marketo know whether someone is registering multiple people using their own email address, and only then switch off deduplication. The only thing you could do is deduplicate by email address and last name (or something similar), but that introduces a host of other issues.
In short: I would start with putting a disclaimer on the thank you page: "If you register multiple people, do NOT use your own email address every time. We need 1 unique email address per registration".
Hope that helps.
Thanks for all the replies. As tech support summarized "there is no server side verification", which limits the use of forms for this type of activity. It appears that it would not be recommend that Marketo forms be used for any type of event registration.
In addition to EventBrite would be interested what anybody else has used for event registrations integrated with Marketo or Salesforce.
We've only used EventBrite, but Marketo doesn't offer an adapter, so we use the EventBrite Import app for Salesforce. It's good, but far from an ideal solution. Marketo uses RegOnline for their Marketo Summit and it would be interesting to hear how they use it with MLM and what their experience has been. I've also seen Cvent used by a few other companies and if you are using Wordpress CMS, there is the free Event Registration plug-in.. Here is a review of some of the systems, but it's from August 2011 A Few Good Online Event-Registration Tools.