I'll say this from experience.. a lot experience.. Don't ask.
The online adult market won't adopt Bitcoin easily. The type of person who buys online porn is a 'revolver' of credit. They don't have money to spend on porn. They *need* credit. That's why credit cards work so well.
Bitcoin is too difficult for the average guy to use. He wants porn. He doesn't care about hashing/encrypting/p2p. No amount of convincing will tell him that Bitcoin is better than a credit card. Also, the thought of downloading and installing an application is scary to an experienced porn customer. They've all had their fair share of viruses, excessive popups from CJ sites, and other general web annoyances.
Porn sites won't adopt Bitcoin because it is a waste of time. It can't do recurring billing. That is their bread and butter. Being able to silently just keep billing someone's credit card, until they cancel, is what fuels their affiliate programs and their promises to pay $150-$200 per sale (aka "join") to affiliates.
Lets say that you solved some of these problems by directing porn customers and merchants to a web interface system like MyBitcoin. Let's also say that they have a working shopping cart system for the merchants. I'll explain the problems with that next...
You could get porn customers to use it. But, you'd end up with the problem of funding the wallet. Assuming that the customer doesn't easily give up. (They *buy* porn because finding it for free is too much of a hassle. They are *LAZY*.) The customer will seek out PayPal or credit card to Bitcoin exchangers. (They stick with what they know.) The liabilities would be held by the exchangers. The levels of chargebacks will slowly increase on these exchangers until they are out of business.
After that happens, it would grind to a halt. Merchants would drop it like a hot potato. They are used to dropping payment options. It is their first reaction when something goes wrong. The online adult industry is riddled with bank/Visa/whatever freeze-ups.
From the merchant side, you'd have the problem of "cashing out". The porn merchants don't give a damn about your virtual currency. They want dollars. MyBitcoin, in this example, would have to guarantee to buy (under contract) every single Bitcoin or no merchant in their right mind would use it. Sure, they could pass the Bitcoins to their affiliates/promoters to alleviate some of their liabilities. This would require some serious adoption (and convincing) across the entire industry.
The only viable option for Bitcoin in the adult arena is the micropayment one. Period. You'd have to supply absolutely *all* of the web technology. (Customer AND merchant.) It would have to be entirely web-based. You'd have to guarantee, in writing, to buy each coin back. This would only work on a few sites. Sites that sell porn per image, video, software download, etc. Sites that don't rely on recurring revenues.
Personal reservations aside; the fastest way to encourage adoption would be a dumbed-down HYIP.