In complaining about the lack of data around his advertising campaigns, legendary Philadelphia merchant John Wanamaker famously once said, “Half the money I spend on advertising is wasted; the trouble is I don’t know which half.”

If Mr. Wanamaker had lived to see the rise of Google and pay-per-click (PPC) advertising, he likely would have been quite pleased.

By leveraging data — specifically, the search query of a Google user — Google now ensures that advertisers are only paying for relevant leads, thus solving Mr. Wanaker’s problem for a big chunk of advertising spend.

The event world is operating much like online advertising prior to PPC.

Without behavioral data about how event attendees are engaging with content, exhibitors, and each other, event organizers have no choice but to rely on hunches to determine how to deploy events that generate maximum return on investment (ROI) for their exhibitors and sponsors.

The good news is that the event world’s “Wanamaker Moment” may soon be here.

The rapid proliferation of smartphones has surpassed anything the world of computing has ever seen.

Today, virtually every event attendee is walking around with a powerful handheld computer that is capable of measuring their engagement before, during, and after the show — and, more importantly — transmitting real-time data back to the event organizer.

To put things in social networking terms, consider the live event as an interest graph in which attendees can be mapped to content, speakers, exhibitors, and more info based on their actual activity.  Smartphone activity can illuminate the nodes and links that comprise this interest graph.

With the devices in place, it is now up to event organizers to figure out how to engage attendees on their smartphones.

One simple tactic that event organizers can take to encourage attendees to leave a digital trail of their interests is to go green and make the hard cut over to digital content in the form of a mobile app.

If there is no paper guide available, attendees will have a compelling reason to access info on agendas, speakers, and exhibitors on their phones.

Event-related content, of course, is just the beginning.  Networking functionality, promotions, communications, social media integration, and presentation collateral are all reasons for attendees to put down the paper and start interacting with a mobile application.

Aggregated together, these interactions will tell the event organizer which content and speakers are resonating with attendees and which are not.

At a more detailed level, individual attendees can be mapped to particular objects – content, speakers, exhibitors, products, and more.

Why does this matter? More leads can be uncovered for exhibitors, attendees can be better segmented by interest, and event organizers can get to know their attendees in order to better serve them.

Much like web analytics packages can help marketers optimize their websites for conversions, so can mobile apps help event organizers optimize their events for ROI for each of the principal stakeholders.

But in order for this to happen, event organizers must learn how to engage attendees on their smartphones.