Scanning the magazine rack at a public library recently for the latest copy of Minnesota Monthly, a regional-interest magazine, I spied a copy of the National Review out of the corner of my eye. On the cover of the right-wing publication loomed a huge, half-wrapped granola bar, along with the piquant headline ?Granola Conservatives: A report from the ?Crunchy Right.??

Intrigued, I grabbed the magazine and read an article detailing the small but growing number of conservatives whose views, including a fondness for locally grown produce and environmental conservation and an antipathy toward suburban sprawl, are almost indistinguishable from those of many liberals.

Pleased by the discovery, I sat back and marveled at what was truly a moment of serendipity. I had shifted my field of inquiry from local bed-and-breakfasts to conservative politics in less than a second, simply through happenstance.

Unfortunately, warns University of Chicago law professor Cass Sunstein, this kind of chance encounter probably wouldn?t have happened in cyberspace. In his book republic.com (Princeton University Press), Sunstein warns against the unintended side effects of personalization software, an emerging technology that allows consumers to filter what they see, read, and listen to according to their own select tastes.

Already, newspaper Web sites operated by the Wall Street Journal, Los Angeles Times, and Christian Science Monitor encourage readers to ?decide what?s news,? as do cable news networks like CNN and MSNBC. And, sites like Sonicnet.com let you create ?Me Music,? your very own musical universe consisting only of songs you want to hear. Never want to hear R & B? No problem. International politics makes you snooze? You can sweep it under the rug forever. You only want to read sports, sports, and more sports? Done.

With just a few mouse clicks you can create ?a communications package that is personally designed, with each component fully chosen in advance,? says MIT professor Nicholas Negroponte, what he calls ?the Daily Me.? Some people celebrate this capacity to weed out entire categories of news, music, or culture; it?s merely an efficient tool, they say, to save precious minutes lost each day in paging through the newspaper or tuning the radio dial.

For others, inhabiting a world entirely of your own making sounds like an isolating experience, bereft of illuminating random encounters and contrary opinions. Hearing only your own voice, or worse, ?louder echoes of your own voice,? as Sunstein puts it, could become somewhat suffocating. He praises the Internet as a tool that ?greatly increases people?s ability to expand their horizons,? but he cautions that ?many people are using it to produce narrowness, not breadth.?