Paul Collins recently asked this question for Slate.com:
Ask anyone under 30 about phone books, though, and you might as well inquire about Victrola needles. The Yellow Pages Association claims that even young households use them when the occasion—a wedding, for instance—demands reliable listings. But printed phone books are a maturing industry, with only about six in 10 businesses and individuals still regularly relying on them. Yet even as directories hemorrhage content to the Web and to unlisted cell numbers, enough oldsters—those, say, who still recall physically dialing numbers in a rotary motion—continue using them enough to keep profits rolling in. In other words, you remaining four in 10 recipients can expect a lot more doorstops and spider-smashers in your future.
Meanwhile, the very first phone book, which Collins also mentions (“We’re a long way from 1878, when New Haven phone subscribers received a single-sided sheet with all of 11 residences and 39 businesses on it.”), is going up for auction at Christie’s. Auction estimates are $30-40K.