PALO ALTO, Calif. (CNN/Money) - When America Online announced its acquisition of Time Warner in early 2000 the opinion by what I like to call the "smart money" was unanimous: This was a terrific deal for AOL shareholders.

After all, they were using over-inflated currency to buy the hard assets and trusted brands of a great, if somewhat pokey, company. (For Time Warner shareholders, of course, the opposite was true.)

Steve Case's resignation Sunday as Chairman of AOL Time Warner just three years later reminds me how important it is to listen to dissenting voices. (Though just about all of Wall Street's best minds completely missed the financial turnaround at Kodak, the best-performing Dow stock of 2002.)

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My first big lesson in this was the 1997 acquisition of U.S. Robotics, then the leading maker of dial-up modems, by networking equipment maker 3Com. After severe initial misgivings, the Street generally liked the deal. But modems were a commodity, the smart set argued, and all 3Com was doing was ensuring that its revenues would become less and less profitable.

The stock plummeted months after the merger as the rest of the world figured out what the skeptics said all along -- that 3Com had invested in the wrong part of the networking industry.

When it came to AOL, the hecklers were loud and clear: Subscriber rates would plummet. Dot-com advertising deals couldn't last. Broadband was a long-term threat. AOL TV (remember that?) was more science project than business plan.

That was all happily ignored by investors seduced by the dream of synergy. Think of yesterday as the day the last nail was driven into the synergy coffin at AOL Time Warner.

You should also take note of what some top naysayers are saying about Hewlett-Packard -- they've hated its acquisition of Compaq from the very beginning. These days a number of top analysts have begun talking about HP as a value play because it has gotten so cheap relative to its peers.

But you'd still be hard pressed to find real champions on Wall Street of HP's strategy. "Does one big heavy rock fall any slower in water than two littler ones?" asks one of my favorite spitballers? At some point the cost cutting will be over and HP will have to deliver. Could it work? Sure. But the smart money won't admit the possibility for some time to come.

So all of this raises the question of what the smart money thinks about AOL Time Warner today. "Now it'll revert to the kind of cash-flow business it was before," predicts another skeptical source, who doesn't invest in large-cap stocks and therefore wouldn't touch AOL.

The consensus, however, is that eventually -- perhaps after an AOL spin-off, definitely after AOL is removed from the company's name -- the owner of magazines, film studios, record companies and cable networks will once again be a popular investment among folks who like steady, profitable media and entertainment companies. (I'm an employee and a shareholder of AOL, by the way.) That's not nearly as exciting as synergy. But it's a whole lot more comforting.

Adam Lashinsky is a senior writer for Fortune magazine. Send e-mail to Adam at lashinskysbottomline@yahoo.com.

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