Optimism is back -- we're sure of that.

Up for debate is whether that optimism is the real deal, or just a head fake that's bound to peter out.

Private equity king Blackstone (NYSE:BX) gave an indication of the latter yesterday. In an internal letter, CEO Steve Schwarzman said his views on equity markets had taken a turn for the better, setting Blackstone up to possibly sell eight of its portfolio companies through initial public offerings. "We see the world changing once again. At least for private equity, the worst is behind the industry" said Schwarzman. "The equity markets are wide open for us right now" said President Tony James last month.

Well, that's just wonderful. But to be fair, private 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 couldn't get its hand on enough huge deals during most of the boom years. Yet in 2007, as financial tremors began shaking, it started pulling back. As Tony James noted in an August 2007 conference call: "In terms of new investing, I think, we stayed very disciplined this year. In fact, we found the first half of the year extremely frustrating, as we [were] routinely outbid by 10% to 15% by other bidders [on] companies that were for sale."

Staying "very disciplined" is a courteous way of saying "this market has lost its mind, and we wouldn't touch it, even with your money."

But that didn't keep management inactive. Knowing the top was near, Blackstone made one of the smartest moves in business history: It sold itself, IPOing in June 2007, right at the top of the top, making its managers astronomically rich. Within 18 months of cashing out from the IPO, Blackstone shares fell over 80%. These aren't stupid people. And that doesn't bode well for markets in light of that same management's current IPO ambitions.

Granted, back in May, I warned that banks like US Bancorp (NYSE:USB), Capital One (NYSE:COF), Wells Fargo (NYSE:WFC), and Morgan Stanley (NYSE:MS) frantically selling stock to public markets wasn't a good sign. Since then, shares in all these companies have moved higher, so obviously the theory isn't bulletproof (at least not yet).

But the idea holds true: When extremely smart, diligent, in-the-know, seasoned investors are eager to sell, it typically doesn't signal the birth of a bull market. Whether it's different this time around is to be seen.

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Fool contributor Morgan Housel doesn't own shares in any of the companies mentioned in this article. The Fool has a disclosure policy.