No big shock here, but some good info for people in the business of marketing...
And on a related note, even if you're not in the "adult" market, you still have to respect these guys for blazing the trail of new technology and online marketing techniques. It's a crowded marketplace and these guys are sharp when it comes to getting visitors and converting them into customers. Sure, it's like selling crack and it's a huge market, but when there is this much money to be made, there are a ton of big players you have to go up against.
I highly recommend subscribing to AVN for some great marketing insights.