Malcolm Gladwell made millions of dollars writing a best seller, The Tipping Point, which described how certain ideas and products catch on rapidly, almost like epidemics. In business, Apple did that with a music-playing virus called the iPod. Now wires dangle from everybody's ears.

In our personal lives, we too have tipping points. At age 50 or beyond, you tip from clued to clueless by making cultural references that cause younger people to glance at each other, as if to say, "Did he just say that? Act polite."

I stepped deeper into the realm of cluelessness by asking a college-age acquaintance why he never answered e-mail sent to his Hotmail account. Lame! (Even that is an outmoded expression.) I had no clue that many young people let Hotmail accounts languish while swapping messages on Facebook, a social networking website.

My tipping point with Hotmail illustrates an enormous challenge for any business leader who considers the Web as part of his or her marketing. How do you reach customers online? What's the right technology? Microsoft last year spent big on one answer, $6 billion to acquire aQuantive, a Seattlebased leader in online advertising. Microsoft now has new tools to go online to see you, touch you, sell to you.

Sorry for the lame reference to "Tommy" and The Who, but I love what Microsoft CEO Steve Ballmer later said about the acquisition: "What's the joke about the egg and bacon breakfast, 'Who's more committed, the pig or the chicken?' We're the pig at the breakfast; we're committed to the future of digital advertising." So even Ballmer is guilty of old references - I'm not even sure if it's wise for Microsoft to call itself a pig - but you get the point. Big money. Big commitment. The Microsoft juggernaut rumbles down a new strategic path. Impressive. But wise?

Probably, but not certainly. Not to diminish aQuantive, but if we know anything about technology trends, it's that markets change at a blinding speed and you can easily misjudge which assets are necessary to win. Today's genius is tomorrow's numbskull. Mighty IBM lost a battle in personal computing with Microsoft. Bill Gates is determined that his company ride what he called the Internet tidal wave and position itself at the center of digital services. One early move on this front came in 1997, when Microsoft bought Hotmail for $400 million and built a base of an estimated 280 million customers. But now, Hotmail and the like are losing popularity to Facebook, MySpace and other social networking sites. MySpace had 20 million visitors a month in 2006; last year, that number exceeded 110 million visitors a month.

So if you're a lawyer in Spokane or a restaurant owner in Yakima, how should all this affect your marketing? Cancel your listing with Yellow Pages? Put all your money into online banner ads? If only it was that simple. Marketing today is increasingly complex, with audiences fragmented across different media. From the pig's perspective, it's nice to have a big checkbook to hedge his bets. After buying aQuantive, Microsoft spent another $240 million for a minority stake in Facebook.

The challenge of reaching potential customers is as old as business itself. It's not getting easier. The only thing certain is that tipping points don't stay still. Hotmail didn't exist 15 years ago. Now, it's going gray on its sideburns. The new seems old.

And the old seems new. Get ready for a new tipping point in your thinking. A new survey by the Pew Internet & American Life Project says if you want to find 18- to 30- year-olds, one place to look is not just the coffee shop, college campus or Modest Mouse concert. Try that gathering place you knew as a kid, visited with mom, to check out Dr. Seuss. Sixty-two percent of 18- to 30-year-olds say they've visited a public library in the past 12 months. That means they are spending more time in libraries than older generations.