A wise man once asked, "What's the sound of one hand clapping?"

My guess is it makes a sort of muted "whoosh" through the air ... but I've got a more immediate question for you today: "What's the sound of one market topping?"

That sound you just heard was the bull market's last gasp, and you heard it from Blackstone (NYSE: BX) first. As 2009 drew to a close, the private-equity powerhouse announced plans to cash out multiple PE deals it had begun before the crash. Blackstone hopes to unload eight of its subsidiaries via IPO, and another five in transactions direct to corporate acquirers. (The sale of Kosmos Energy's Ghanaian oil interests to ExxonMobil (NYSE: XOM) is perhaps the highest-profile of these exits.)

As Blackstone heads for the exits, enquiring Fools want to know: Is this the beginning of the end?

What's the rush, Blackstone?
Already, Blackstone has pushed hospital staffer Team Health out the door. Underwriters Bank of America (NYSE: BAC), Goldman Sachs (NYSE: GS), Barclays, and Citigroup were undoubtedly pleased with the 7% pop Team Health received on IPO day. But early investors in Blackstone offspring Graham Packaging (NYSE: GRM) have watched their shares idle in neutral since being spun off earlier this month. IPO profits, it seems, are getting harder to come by.

If all this sounds familiar ... well, it should. On March 22, 2007, Blackstone called the top of the last bull market. As with the Team Health IPO, Blackstone's 2007 decision to take itself "public" was well received initially. This was good news, many investors thought -- a chance for everyone to own a piece of the private-equity superstar, and cash in on the booming market for high-stakes corporate mergers and acquisitions. But what individual investors saw as a chance to cash in was actually Blackstone's chance to cash out at the top.

Now it's happening again.

Seismic rumblings
Blackstone's self-IPO didn't ring a bell and spark a sell-off all of a sudden, of course. To the contrary, over the three months from announcement to implementation in June 2007, the stock market continued its inexorable rise. On IPO day itself, Blackstone's shares popped 13%. Even then, it took another four months before the market finally topped out.

From the market peak in Oct. 12, 2007, through its nadir on March 6, 2009, shares of Google shed more than half their value. Amazon.com (Nasdaq: AMZN) dropped by 37%. And as the financial crisis deepened, General Electric's (NYSE: GE) capital finance arm dragged that goliath down by an incredible 81%! Across the length and breadth of the S&P 500, stocks shed more than 55% of their value.

Will history repeat?
In recent weeks, we've seen a marked rise in "red" tickers scrolling across our computer screens. Nothing as bad as the 2007 crash, of course -- to the contrary, over the four months since Blackstone announced its plans, the S&P has actually eked out a 3% gain. Buoyed by the recovery, the Federal Reserve has begun cautiously raising interest rates. But as we saw last time around, Blackstone's IPO activities don't necessarily mark the exact top of a market. They're just one clue -- a hint that we should open our eyes and see whether there's anything else suggesting that the market's gotten a mite frothy.

With this suggestion in mind, I note two other IPOs on the horizon. Blackstone rivals Kohlberg Kravis Roberts and Apollo Global Management missed the IPO window back in 2007. Before they could follow in Blackstone's footsteps, the market had collapsed, and their chances to reap big gains from selling their own shares had vanished. But reports suggest that both P/E firms intend to remedy that mistake this year, floating shares and going public themselves if the market remains receptive.

As the private-equiteers swarm, Fools duel
All of this has Fools engaged in a heated argument over the meaning of these private-equity IPOs.

On the one hand, my Foolish colleague Matt Koppenheffer sees promise in these IPOS: 

[Blackstone's] business is raising funds, making investments, and selling those investments. ... They've gotta realize their investments at some point and the past year or so hasn't given them any opportunities. [The fact that they are choosing to sell now,] I think, says more good about the market/economy than bad.

On the other hand, market skeptic Morgan Housel recently argued: "[P]rivate-equity firms typically relist their portfolio companies only when they think the price is already high, not when it's at a turning point. And nobody has been better at calling the top through IPOs than Blackstone."

Blackstone, green profits
I see merit in both viewpoints. I worry that Blackstone may see something I do not -- but because I know that investing in stocks is the surest way to build wealth over time, I don't want to exit the market entirely. That's why I'm preparing my own portfolio for either option -- both the return to the bull market that Matt hopes to see, and a impending crash that Morgan fears (and that history suggests could happen.)

You see, I believe that by investing in strong businesses with moderate debt loads (or even better, no debt at all), it's possible to both mitigate the damage of a market downturn and participate in the profits if the market maintains its momentum.

And I'm not alone. Over at Motley Fool Inside Value, our dedicated team of value hunters has been building out a portfolio of companies able to navigate any economy -- and any stock market. By investing in market leaders that boast recognizable brand names and impregnable balance sheets -- companies such as Coca-Cola, Wal-Mart, and Microsoft -- Inside Value has helped investors beat the market successfully, in bull markets and bear, for more than five years running.

In a world full of Blackstones, hopping into and out of the stock market and picking your pocket with every step, Inside Value just may be the best friend you've got -- and the best way to profit from the market, whichever way it turns. Click here to try it out, completely free, for 30 days.

Coca-Cola, Microsoft, and Wal-Mart Stores are Motley Fool Inside Value picks. Google is a Motley Fool Rule Breakers selection. Amazon.com is a Motley Fool Stock Advisor recommendation. Coca-Cola is a Motley Fool Income Investor selection. Motley Fool Options has recommended a diagonal call position on Microsoft.

Fool contributor Rich Smith owns no shares of any company named above. The Motley Fool's disclosure policy thinks the road to profit is paved with the black stone known as asphalt.