You might say that Taser International (NASDAQ:TASR) has been on a roll. Following yesterday afternoon's stellar fourth-quarter report, Taser shares are up 10% to over $148 midday, meaning this: If you had bought the stock at its 52-week low of $3.65, you'd be looking at a mere 40-bagger.

The maker of stun guns earned $2.8 million, or $0.56 per share in the fourth quarter, up from $0.02 per share the same quarter last year. Meanwhile, sales almost quadrupled to $10.8 million. And here's the kicker: At last count, more than half of Taser's 2.2 million-share float was sold short.

Not surprisingly, doubters point to Taser's 300-plus trailing price-to-earnings ratio. A recent Barron's article even suggested that the company was approaching market saturation.

But Taser insists that 4,300 law enforcement agencies were either testing or deploying its weapons by the end of 2003, including 800 added during the fourth quarter. More than 500 agencies had committed to full deployment, meaning "one TASER on each of their line level patrol officers."

The story gets better. The company has penetrated just 24% of U.S. law enforcement agencies, and "only 5.2% of the available market of individual officers in the United States." Not only does that leave room for growth in law enforcement, but there's also the U.S. military. And yes, Taser points out, there's the rest of the world.

Based on this, Taser expects revenues to double in 2004, which implies revenues of around $50 million for the current year. And given the fourth quarter's earnings results alone, I think it's a pretty fair assumption that earnings will climb even faster than that.

Back in October, Fool Dave Marino-Nachison thought the stock had some room to run near $51 per share. Last month, fellow Fool Seth Jayson still didn't think Taser shares were unreasonable at $112. But near $150, the picture gets a little muddier.

Given Taser's explosive growth, expanding opportunities, and clear realization of its earnings potential, I can't say that Taser's shares are so richly priced that I'd bail. But if you're looking to buy with a margin of safety, I don't think you'll find a whole of that here.

Give us your take on the Taser International discussion board.

Jeff Hwang can be reached here.