Write what you know was emblazoned on many blackboards when marketers went to school, especially those who combined journalism and business. To evoke passion in their writing, instructors urged beginning writers to stick to topics they were passionate about.

And then one day those writers were assigned a campaign on kitty litter scoops or plumbing.

If you were that writer, you increasingly found yourself writing what you knew to the wrong audience. Nothing brought that lesson home harder than my son’s 21 year old girlfriend, who was shocked to hear me say that Paula Abdul was once a hottie. In her experience, Paula is a shlocky celeb-wanna be who sits between an acerbic British music maven and an affable American music maven on a hit television show.

Even if she knew that Paula Abdul was once a recording artist, Paula is to her what Petula Clark was to me – a successful singer my parents listened to when I was a toddler. She had no image of Paula writhing around a soundstage to the thumping sounds of Cold Hearted Snake or appearing next to a dashing Keanu Reeves in the Rush Rush video.

In writing what I knew – that Paula Abdul was one of the best selling artists of the mid 1980s, that she was Janet Jackson’s choreographer and that she was married to Emilio Estevez (Who? Oh, Charlie Sheen’s brother) – I contradicted her notion of Paula Abdul. Her experience of Paula Abdul is as a national punch line who causes people to wonder whether she has a substance abuse problem. Even the credibility of Janet Jackson’s accomplishments were washed away in this young woman’s mind by Jackson’s unfortunate Super Bowl appearance.

Writing what I know is wrong for most of today’s market. If my target is a wireless device or a review of a hit television show, my cultural touchpoints must be current. So must my language. And in our world of constant information consumption, making a point fast runs counter to the four and five page direct mail pieces most of us remember.

That means the pace, style and tone must be relevant too. Strunk, White and Edwin Newman can all take a backseat in my hybrid because while I write for boomers, I also must write for millenials, and they don’t know Edwin Newman. Some are having a hazy time with Dan Rather.

Dennis Miller didn't become irrelevant because his politics shifted. He became irrelevant because he really didn't mean it when he exhorted audiences to "Stop me before I sub-reference again." They didn't, he didn't and now he doesn't.

I wrote a draft last week for a heating contractor and used the headline, Baby, It’s Cold Outside. Nice, except a 60 year old standard has no place in a campaign where my average buyer may not be a millennial, but if they were born after 1970 or so, they are reading a title with no meaning and certainly not evoking the same emotion my grandmother would have experienced.

None of this is new. I imagine marketers go through this change each generation. But the time is compressed now, and if there were once 15 minutes allocated for fame, a web world with a global scope has shrunk the number to 10 or 12 minutes.

Once you learn how to write, don’t write what you know.

Write what they know.