(Beam acquisition story, updated to reflect additional analyst comments and additional data)

NEW YORK ( TheStreet) -- William Ackman's favorite market drink, whiskey maker Beam ( BEAM), is buying vodka and rum brands from privately held spirits company White Rock Distillers, a deal that nearly doubles Beam's presence in the Vodka market and diversifies its top shelf, but could sober up shareholders betting that a takeover offer is coming.

Beam's acquisition of the fast-growing Pinnacle Vodka brand and a line of flavored rums called Calico Jack's, is the whiskey maker's biggest move so far as a stand-alone purveyor of spirits. Beam was spun out of Fortune Brands ( FBHS) in mid-2011.

The $605 million acquisition may dim speculation that the maker of Jim Beam and Makers Mark whiskey can be acquired by a spirits giant like Diageo ( DEO), market chatter that began after the 2011 spinoff.

"With Diageo widely considered to be the most likely acquirer, this purchase presents another hurdle in terms of a take-out, in our opinion, as BEAM's larger stake in the vodka category creates another area of overlap with Diageo (the market share leader in the U.S. vodka category)," wrote Citigroup analyst Geoffrey Small in a Monday research note.

If a recent shot of premium in Beam shares wasn't justified by the likelihood of a takeover, the deal could be the beginning of headwinds for the company's stock.

"The company's shares have been driven up well above their fundamental value, in our view, by bid speculation," wrote Ian Shackleton of Nomura Securities in a Monday note. Such a deal with Diageo is likely off the table because, "Diageo would not be allowed to keep the Pinnacle brand, we believe, given its already high share of U.S. vodka."

Beam's shares have rallied strongly, posting over 25% gains since its September IPO. However, Small notes that speculation of a takeover drove at least some of those stock gains. "BEAM's shares are currently trading at a fairly rich 14 times second fiscal year price to earnings multiple , reflecting the acquisition premium built into the stock."

In early Monday afternoon trading, Beam shares fell more than 2% to $55.66, double the broad market loss and outpacing the decline in consumer stocks. The decline cut into Beam's year-to-date gains of roughly 10%.

The spinoff came at the urging of activist investor Ackman, who is currently the single largest shareholder in both companies. The spinoff and Beam's initial public offering separated Fortune Brands home and security unit from its alcohols business, creating two separate publicly traded companies with a distinct focus.

In March, Goldman Sachs reiterated Beam as a potential target of a large acquirer in an update on a basket of stocks that its "tactical research" team considers M&A candidates across all sectors. Goldman lists Monster Beverage ( MNST) as its newest takeover target in the beverage sector in the report.

Analysts polled by Bloomberg give Beam shares an average price target of $56.11 on 21 buy ratings and five holds to go with two sell ratings.

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