I'm talking about trade shows, SXSW, street marketing…
There are two ways to be glad you went:
1. An overwhelming show of force. When you have the biggest booth, when you are the buzz of the event, when you are everywhere people look, you reinforce your position as the leader.
2. Powerful personal interactions. Not with everyone. Just with people who want to talk with you, who will benefit from a powerful exchange. Not mass, but high in value. Even better, designing these interactions (and your product) so that this small number of people set out to evangelize their peers on your behalf.
The mistake almost everyone makes is to do both. Or to believe that they know a cheap shortcut on their way to #1. Or to get too busy chasing (and failing) at mass that they don't have time to do the personal.
Years ago, the company I worked for spent millions at various venues of the Consumer Electronics Show. We were there, we were sort of big and we sort of won. But not really. Too much noise, too much competition, we were neither. By trying to reach as many as we could, we were never intimate enough to generate conversations that mattered or ideas that spread…
Once again, it comes down to scale. If you staff and invest appropriately, you don't have to 'win' the show to make it worth the trip. On the other hand, if you're setting out to win and investing at the appropriate level, you better win.