I see this a lot - if you like this story, please share it with friends.  You can email the link to your friends (with a neat customized message), or  share the link on delicious, facebook, digg and other social networking sites.  Yes, you can do this within the registration process, but, as event planners, wouldn’t you rather already have the data than rely on your attendees “friends” to fill it out??

Expand on this feature - integrating it within the registration process, rather than an afterthought.  Ask the attendee to enter in their friends / colleagues information -  name, company, job title, phone and email.    Anything more than that may seem like too much work and act as a deterrent.  Anything less and you may lose some critical information.    But, you would have the data.  They can always update their information later - filling in everything else that is required in the registration process and entering in the individual demographics  (company-level demographics can be already copied over) .  Yes, you can make the argument that these people didn’t register themselves for your event and therefor they shouldn’t be counted.  I am not saying that.  Get them in the system, market to them, confirm them, badge them, whatever.  Our sister company, CrossTech Media, owners and producers of the Itec events have implemented this with success this past fall.

Remember, only a registered attendee can show up.