A third option is to include a custom field with a "Where did you hear about this event?", including a drop down menu with options like "Talend Invitation", "Partner Invitation", "Friend or Colleague Referral", Social Media, etc.
The upside is that you might identify those who heard about the event via a partner, but came directly to your website to register (and vice versa). Plus its a bit richer detail on orginal source (as opposed to registration source).
The downside is you rely on the individual to give you an answer.
You could combine this approach with either of Josh's ideas to give you more intelligence on where your leads are coming from and how theyr'e learning about your events..