Arianna Huffington's web venture is finally in the black. It only took five years, thousands of volunteer bloggers and the most clever search engine optimization that money can buy.

The Huffington Post sounds like it has been transformed into a veritable money machine; it turned profitable in the second quarter of this year and is on track to triple revenue in 2010, with a goal of doubling it in 2011, according to a story by Gawker founding editor Elizabeth Spiers in Forbes. Much of that growth is expected to come from selling sponsored posts that essentially rent out HuffPo's impressive Google juice to advertisers.

For all its buzz and traffic — up more than 80 percent this year — profitability was elusive for HuffPo, no doubt partly because Arianna is a spendthrift with expensive corporate tastes, her controversial army of unpaid contributors not withstanding. But Spiers raises other good reasons HuffPo spent so long in the red: It's hard to sell advertisers on people arriving from Google, from Facebook, and for the political content that's so popular among HuffPo's die hard readers. Yet the site has somehow finally managed to deliver on all those recent promises of generating money. Thanks in large part, surely, to the sheer size and speed of its traffic growth. Hopefully for Arianna and her venture capital investors, the magic that finally converted all those eyeballs into ad revenue is both sustainable and scalable.