Dr. Mohamed Damak, a ratings specialist at Standard & Poor's, notes that he has "clearly noticed a shift in the structures of sukuks issued in 2008 toward Ijara (where financing is accomplished through a form of sale-lease back of real assets) away from Musharakah (a more controversial form of profit-sharing questioned by Islamic scholars).

Even without the religious controversy, questions remain as to whether sukuks might ever grow beyond being a niche product, since Islamic law prohibits them from being tranched (sliced up into different yields) or effectively hedged.

Professor Samuel Hayes of Harvard Business School notes that the prohibition on hedging means that any financial arrangement that could be affected by changes in exchange rates or in the rate of inflation leaves the investor "vulnerable to a very substantial risk."

They also have yet to be tested in a default. Warde says this is among the chief concerns for the market going forward. Although sukuk issuers have tried to devise asset liquidation mechanisms that dovetail with those found in conventional bonds, none of these have been tested in court.

"The main fear that investors have is what will happen in practice if some sukuk goes bad," he says. While most Islamic contracts now prescribe English law to be governing, Warde says that "in the case of failure of sukuk, the process of adjudication will be a complex and long-drawn affair, whereby judges will want to know what sukuk really are, and as part of that process, Shariah scholars will no doubt have some input."

With easy credit and oil powering the Gulf real estate markets to dizzying heights, such defaults might come sooner than anyone thinks, making the Shariah scholars among the hottest commodities around.

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