This can happen when someone registers multiple people for the same webinar, especially if you have a progressive profiling form that doesn't display the name and company fields the second time a form is displayed after the initial registration.
To help prevent this, don't use progressive profiling forms for event / webinar registrations. Then the initial registrant returns to the form, the name and company fields will be displayed and the registrant can update them along with the email address.
you will increase your odds of getting an accurate new lead record created each time someone fills out the form for someone else if you disable pre-population into these fields using the instructions in the
Disable Form Prefill help article..
Finally, the tracking cookie that is left on a user's system will be based on the lead created in the last form fill, which may not be that person's system, so you may want to consider disabling the creation of cookies by removing the Munchkin tracking code on the page using the instructions in the How to remove Munchkin from landing pages help article.
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