Reports that private equity group Blackstone is working intensively on an initial public offering of up to 10% of the firm continue to tantalise market watchers. It has been estimated that a public offering could value Blackstone at more than $20 bn. Yet, Stephen Schwarzman, Blackstone's ceo, is on record as promoting the merits of staying private. His company has spent some $160 bn in the last two decades to take companies to revamp them and later sell them at a profit. Back in February, Blackstone acquired Equity Office, the largest office landlord in the US, for a record $38.9 bn in the largest real estate deal in history.