Sitting next to Serge Milman in Broadway's trading room is Steven Girden, 36, a former o-t-c marketmaker at Bear, Stearns' risk arbitrage desk.

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That led to risk arbitrage and some small-time buyouts.

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But my best guess is that someone on that risk free arbitrage desk moved from risk free pure arbitrage into very definitely not risk free time arbitrage, or speculation as we should call it, then the market moved against his bet.

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This risk-free arbitrage trade locked in a small profit for the institutional investor and kept the SuperUnit market price in line with its underlying value.

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However, one of this summer's best investment tips, currency arbitrage, is risk-free.

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Terry adds that recent Google policy changes create the risk of additional restrictions around redirection and arbitrage programs.

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But unlike closed-end funds, if SuperUnits developed a discount to its underlying securities value, then institutional investors could arbitrage the units and profit risk-free.

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Hence, a key objective for mobile operators is to rebalance their tariffs to remove an arbitrage opportunity: to move to integrated tariffs and cut out this risk.

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