Business cards are the single most cost-effective marketing tool you can use. It's not about collecting and handing out mass quantities of business cards. The actual cards are just pieces of paper. The real value is the people who are represented by the information on the cards.
Carrying business cards is a no-brainer. Without a business card, how will contacts know how to reach you? It's your calling card for your professional life. Even though they can be ordered in large quantities, it's not quantity that leads to a profitable network, so use cards wisely.
Among negative networking connotations is the image of a salesman walking into a function and handing out his card randomly to absolutely everyone who walks through the door. What are the chances those people will call him? Slim to none. In North America, the appropriate exchange of business cards is between two people who have met, had a conversation, and created a mini-bond.
There are some who defend the position that they won't give out cards; they will only take cards so they can control the follow-ups and avoid hearing from people they don't like. This seems shortsighted to me. If you receive and give a card you still have the same control. Sure, every now and again you will give your card to a person who will follow up repeatedly and add you to mailing lists without your permission. Just unsubscribe. That's a risk of doing business and that's why you have technology with spam controls.