You definitely need a business card. And you should definitely carry some with you wherever you go. But you should most definitely not hand them out indiscriminately.

In an interview with WalletPop, Chris Brogan points out that handing out your business card before you've engaged with someone — i.e. have had a conversation with him/her — is pointless. How is that person going to know whether they want to do business with you? What reason do they have to contact you? "Don't collect them just to collect them," Brogan says. "There's no value in collecting business cards."