This probably varies from country to country, but given that business cards can be had for the cost of running off-the-shelf preperforated stock through your computer, I think it's worth having a few. It does make handing your contact info to someone easier, plus giving you and/or them a surface upon which to scribble a note about why they should contact you.
And at least around here, many restaurants collect business cards as tickets for a free-lunch lottery. Trade shows may also use them as lottery entries.
Yes, e-mail addresses are starting to replace business cards as e-mail becomes an acceptable replacement for postal mail and phones, and smartphones can be used to enter contact info into a website.... But it isn't a complete replacement yet, and may never be.
And I find I use them informally as well, when I want someone I've just met to contact me about something.
Recommendation: Spend a small amount to print off a few, see how quickly you're using them, use that to guide how many more you obtain, how often, how many you should bother carrying at once, and how much effort you should put into the card's aesthetics.