You should regard picking up a business card at a conference as a sign of failure. It means your online networking is not working as it should.
These days there is no excuse. Twitter sends you three people you should connect with every day, LinkedIn has oceans of suggestions (not all good ones, but they're there) and there are a host of sites like this one dedicated to helping you find the people making waves in your space.
There is a second factor - what you do with them.
In the 19th century people collected stamps. They knew nothing about them, just put them in an album to show off how many they had.
In the 20th century people did the same with business cards. In an era where finding out about what was out there was hard, contacts were important. But with the advent of the telephone, it became much easier. Sales people would build massive Rolodexes of contacts to show how important they were and send a message to their boss - if I go the Rolodex does too.
The boss's reaction was CRM. The boardroom feeling was that those contacts belong to the company, not the person and every salesperson was forced to divulge details of every interaction to the system.
But many people haven't got out of the stamp collecting mindset. They collect cards just to feel connected, to show off how many people they know. And they do nothing with them - simply show them off like trophies in a cabinet.
So ask yourself three things.
1. Why have I not met this person before?
Are they Luddites who don't show up online? If so why am I bothering with them - they aren't the best people in the industry. Perhaps they're new - maybe they've moved jobs - in which case I'd better dig behind the current card to see their track record. Who do they know that I know, so I can triangulate to learn more about them? But really I should have heard of them in their old guise - perhaps they don't know this industry but are just out to make a quick buck. Alarm bells should be ringing. Why were they recruited, what's their remit etc.
2. Who else do I know at this organisation?
Regardless of the person, you should surely know all the companies and players (regulatory bodies, funding groups, media etc.) in your space. How good they are, how close to what you're doing, potential for co-operation, collaboration or competition. Basically what you can get from knowing them and them knowing you - both long and short term. So who did this person replace, and where is he/she now? Why did they move on and what does that tell me about the dynamics of the company?
3. The Biggie. What can I do now to make use of this contact?
What can I propose to them? How should I tease this out? Is something going on I should nip in the bud, or get involved in? Why have they suddenly surfaced - is there a new initiative? And how much time and effort should I expend - are they just a nice to know, or a must get involved with?
With a modern intelligence system, you know your market. Not only what is happening today, but who are the players sitting on the subs bench, waiting to come on. Shows are not part of that intelligence gathering system, they are only the confirmation of it - the place to go to renew old acquaintances, tease out the intel, have some face time and watch the tells to see what is really going on. If you are relying on finding out something new at a show, you really shouldn't be in that industry at all!