In my experience this isn't obvious to most. I've hosted an event 8x a year since 2000, and you can see the people who seem to be 'on a mission' as opposed to the ones that are a bit more subtle about it. If it takes you less than 5 seconds to produce a business card, you're probably a bit too anxious.

Many people view events as an almost speed dating type atmosphere instead of just staying in the moment and not fixating on the need to acquire (info, contacts, etc.).