The $315 million that AOL is paying for The Huffington Post is roughly three times the valuation seen at its last capital raise two years ago, and is 10 times its 2010 revenues and roughly five times estimated-forward 2011 revenues. Those are all big numbers, but not insanely so, for what is clearly a big strategic move on the part of AOL. After all, AOL has a market cap of $2.3 billion: right now it still dwarfs HuffPo. That might not be true in a few years’ time, if HuffPo continues growing at its current rate and AOL continues to lose subscribers and revenues.

My feeling, then, is that this deal is a good one for both sides. AOL gets something it desperately needs: a voice and a clear editorial vision. It’s smart, and bold, to put Arianna in charge of all AOL’s editorial content, since she is one of the precious few people who has managed to create a mass-market general-interest online publication which isn’t bland and which has an instantly identifiable personality. That’s a rare skill and one which AOL desperately needs to apply to its broad yet inchoate suite of websites.

As for HuffPo, it gets lots of money, great tech content from Engadget and TechCrunch, hugely valuable video-production abilities, a local infrastructure in Patch, lots of money, a public stock-market listing with which to make fill-in acquisitions and incentivize employees with options, a massive leg up in terms of reaching the older and more conservative Web 1.0 audience and did I mention lots of money?

Last year at SXSW I was talking about how ambitious New York entrepreneurs in the dot-com space have often done very well for themselves in the tech space, but have signally failed to engineer massive exits in the content space. With this sale, Jonah Peretti changes all that; his minority stake in HuffPo is probably worth more than the amount of money Jason Calacanis got when he sold Weblogs Inc. to AOL.

And then, of course, there’s Arianna, who is now officially the Empress of the Internet with both power and her own self-made dynastic wealth. She’s already started raiding big names from mainstream media, like Howard Fineman and Tim O’Brien; expect that trend to accelerate now that she’s on a much firmer financial footing.

Most interestingly of all, however, is the way that AOL is creating a new entity, the Huffington Post Media Group, to run all of its content business. Given that AOL CEO Tim Armstrong has repeatedly talked about how he wants to be a content company, one has to wonder what that means for the rest of AOL — a group of businesses that still throw off the vast majority of the company’s revenues but are strategically non-core.

The question now has to be asked: is AOL really the right parent for the unique and very valuable Huffington Post Media Group? My guess is that as AOL continues to divest itself of non-core assets, HPMG will make it increasingly attractive as a takeover target itself.

HuffPo was definitively sold off today. But it might wind up getting sold again in the none-too-distant future.

Felix Salmon is a finance blogger at Reuters, where this column first appeared.