So much work. Why is this activity 'passive'??
FB ads are a fun game, cloakers are even more fun. It's a lot of list maint, but once you get a nice ad management system running, things get fun.
I can't (won't) go into details, but I'm currently a dev on a project like this.
edit: Passive in the sense that much of the tedium has been removed, not in the sense that you still don't have to do proper marketing.
That's not "passive". That's "marketing".
I think with the tech industry in general, things move along too quickly for these types of 'passive income' to be stable for more than a few years. After a while, if you're not keeping up with the changes, the stream will die out. Unlike, say, passive investments in the stock market (although there's more volatility there, of course).
Waking up and doing nothing for a few weeks or months doesn't hurt. Making sure you're still relevant in Google, Amazon, App store or whatever your channels is about the same as poking around in your e-trade account and managing some stocks.
If you keep the business small and automated, it's not as unlikely as it sounds. Tech needn't be bleeding edge. The economy is huge and there's a place for solving all kinds of tiny problems. You can still love the business and give it whatever you want, but it doesn't have to own all your creative and mental output.