Is it starting a blog and writing tons of blog posts and monetizing with adsense and affiliate ads?
Is it sending traffic directly to affiliate programs via ppc and other means of traffic generation?
Is it starting up a store selling tangible goods?
Could it be creating a social network and monetizing with ads?
Or creating your own digital information or software product and advertising it and growing your own affiliate network?
I personally think its creating your own digital information product or software product and building your own network of affiliates. When you have your own product, you can buy traffic as long as it costs you less money per click than each click is worth to you. Also, once you have enough websites promoting your product via your affiliate program, you pretty much just have to sit and watch the money roll in.