Blackstone Rocks Wall Street

"The one thing that's bothered me about hedge funds and private equity is there's no transparency," says Muriel Siebert, chairwoman of her eponymous discount brokerage firm and a 40-year Wall Street veteran. "I want to know all the details. How much equity are they putting into a deal and how much leverage and under what terms?"

And it's impossible to ignore that investors are hot for these kinds of companies right now. Fortress shares doubled in their first day of trading on the NYSE, and talk of a Citadel IPO has been swirling around Wall Street as well.

"I think Fortress got everybody thinking," says Siebert.

Adds Menlow, "Appetite for [Blackstone] is going to be off the scale."