Not so - the Yahoo! numbers might be technically correct on a balance sheet but are not economically correct with respect to a share/unit of BX.
The Yahoo! numbers include 9+ billion in "Loans Payable" which are related to CLO's and other investment vehicles owned/managed by the firm, and such debt is non-recourse relative to BX - the investments will either win or lose, but BX doesn't owe the 9B. (It would be like saying that you have $1billion in debt personally because you own a share/unit of BX).
From the latest press release: CAPITAL AND LIQUIDITY As of March 31, 2012, Blackstone had $1.1 billion in cash, Treasury cash management strategies and liquid Blackstone funds.
Long-term debt totaled $1.0 billion in borrowings from the 2010 and 2009 bond issuances.
Blackstone has no borrowings outstanding against its $1 billion revolving credit facility, which expires in April 2016.
BX is actually very (very) conservatively managed itself, but manages leveraged investments for others.