Merrill Lynch (NYSE:MER) and Bank of America (NYSE:BAC) shareholders both approved the latter's acquisition of the former. However, the veneer of formal votes and the hearty handshakes of chief executives mask a critical question: Who got the better deal?

On Sept. 15, B of A CEO and serial acquirer Ken Lewis offered up 0.8595 share of B of A for every Merrill share. At the time of the announcement, that valued each Merrill share at $29. Since then, however, Bank of America shares have shed more than half their value and the original offer is now worth just $13.10, or virtually zero premium to the closing price of Merrill shares on the Friday before the deal was struck. Merrill’s share price hasn’t budged much in the interim.

Why pay a premium for a starving man’s wares?
Those numbers suggest that B of A was inordinately generous, offering a massive acquisition premium for Merrill. Instead, B of A should have taken advantage of the overvaluation in its shares and its position as acquirer of last resort to give up far less of its equity. Remember that the deal was struck the same weekend that Lehman Brothers failed -- Merrill was a desperate seller.

Merrill CEO John Thain, on the other hand, made a smart, opportunistic deal with an overeager acquirer. Merrill’s alternative? Just take a look at its two main rivals: Goldman Sachs (NYSE:GS) and Morgan Stanley (NYSE:MS) have lost more than half their market value since that fateful weekend.

One other constituency is making out nicely: arbitrageurs who bet on the merger and are earning a healthy return. They need it. This year has been downright awful for merger arbitrage, with very low deal volume and large announced deals collapsing (Rio Tinto (NYSE:RTP) and BHP Billiton (NYSE:BHP), for example) or in real jeopardy (the buyout of Canadian telco BCE (NYSE: BCE), which is supposed to close Dec. 11, for example).

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Fool contributor Alex Dumortier, CFA, has no beneficial interest in any of the companies mentioned in this article. Bank of America is a Motley Fool Income Investor pick. Try any of our Foolish newsletters today, free for 30 days. The Motley Fool has a disclosure policy.