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The boo birds are back at Sirius XM Radio (NASDAQ:SIRI). Short interest on the satellite radio provider ballooned to nearly 160.5 million as of mid-August, making it the most heavily shorted Nasdaq stock based on volume.

Sirius XM has always had a high number of shares sold short. The low stock price, prolific name, and history of trading volatility attract speculators on both sides of the fence.

The bearish wagers are likely misplaced. Sirius XM may have gone from being the third most shorted stock on Nasdaq in mid-July to the top dog two weeks later, but it's more likely to burn the bears if it burns anyone at all.

Sirius XM's not as volatile as it used to be. Its beta over the past year is a mere 0.85, according to data from S&P Capital IQ. That's a far cry from its five-year beta of 1.91.

The stock's been bouncing between $3.13 and $4.04 over the past year, a pretty tight 52-week trading range for a stock with such a low share price. When Sirius XM has moved it has typically been painful for the naysayers. This is still one of the market's biggest winners since bottoming out at $0.05 in 2009, a 76-bagger in that time for those scoring at home. 

Shorting Sirius XM is also dangerous because the media giant has shown a hankering for eating its own cooking. It spent $2.5 billion to repurchase 739 million shares, and it has gone through another $1.3 billion to buy back another 388 million shares so far in 2015. Sirius XM's voracious appetite isn't going away. Its board authorized $2 billion more in stock repurchases just last week.

So why are bears so bent on shorting a stock with a low beta and a board-blessed mandate to snap up shares in the open market. It's not as if Sirius XM itself is a flimsy model on life support these days. Sirius XM has rattled off 18 consecutive quarters of profitability. It continues to grow its subscriber base. It's eyeing $1.3 billion in free cash flow this year.

One can argue that 160.5 million shares sold short isn't such a big number with a stock that's trading at a Happy Meal price, but this is actually the highest number of shorts that Sirius XM has had since last November. This would make sense if Sirius XM were heading into some serious headwinds, but that's not the case here. It has overcome the fear that the connected car would make satellite radio a transitory technology. It continues to close every passing quarter with a record number of accounts. The automotive industry -- its primary source for new subscribers -- is holding up just fine. Sirius XM's churn rate is also at a historic low, proving that folks are sticking around in larger numbers after their free trials run out.

You certainly don't have to go long Sirius XM. There are plenty of great growth stocks out there. However, it remains to be seen why shorts suddenly find it so attractive when all it has done is instill six years of regret to those that have bet against the satrad monopoly in the past.    

Rick Munarriz has no position in any stocks mentioned, and neither does The Motley Fool. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.