1. Download site like rapidshare and other crappy host. Inconvenient captcha and required paypal. Bitcoin can possibly take both roles and streamline the whole process. Suggested by Kiba.
That could be an interesting project. I'd be willing to work on the technical side but not sure I really have time to do proper support/marketing. Anyone interested in partnering up?
There will be nothing to market if there aren't anything to market. I suspect it required maybe only a week of development if you're competent. Other than that, it's about gaining critical mass of stuff to download before explosion, I suspect. Marketing can be something like gathering desirable and not illegal stuff to download, curating it, etc and than giving the link to people who want it. That can be done in your spare downtime until you find marketer worth his salt of set up an affiliate program that incentivized people to market for you.
Actually, I didn't suggested it originally, but somebody else did in the thread about p0rn.