I think that this theory applies to highly scalable markets combined with common-purpose products, such as a web app for a certain hobby (e.g., learning to play the guitar). An ad-supported Android app ought to have a userbase of 200.000 - 500.000 users to confidently reach 1000$ of montly revenue - in this case I would say it is highly unlikely that you will ever reach 100.000$ of monthly income (except you write Angry Birds, of course - but they built upon the success of the game on other platforms, a thing an army-of-one could not do within the required timespan). For this exact reason, I consider quitting Android development for the time being.
Many times over, although it seems like everyday I hear of an affiliate marketer who is killing it online and I wonder how.
Having interacted with that world somewhat in the past, I can say that there are some very rare affiliate marketers who are making a good chunk of cash - but those are people who have invested a lot of time and energy into building vast mailing lists of followers who sign up to stuff they recommend.
If you're willing to spend years building such a mailing list, you can make a few thousands a month jumping between various MLM opportunities. Personally, I'd find that deeply unsatisfying work.
As an "army of one" you can be almost as fast as a small team, and you can execute with much higher conceptual coherence. I.e., you can aim better.
It is important to filter out ideas you're not interested in running, even if they could make money.
And once you start getting traction, it's important to focus hard on exploiting it.
Making $1000 per month is harder than scaling that to $100,000 per month (if the market size is large enough).