I wonder where the money I get each month from Google comes from.
Exactly how much money is pouring in from Google every month on those 25+ forums of yours? Roughly. Feel free to round it off to the nearest $100. If it's more than I make at my day job, I'll concede that I'm wrong.
Anyway, my point is not that you can't make
some money from Google ads. I know people who spend a quarter of a million dollars a year on Google ads, so I know
someone is getting paid. The point is those dollars are not going to replace the dollars from a regular job for 99.999% of the people who set up a web site or forum as a potential source of income. I've been working in the web hosting industry for more than 15 years now, and I've seen thousands - no, tens of thousands - of "Woo! I'm gonna be an internet millionaire!" sites started and then abandoned a year later when they don't even bring in enough revenue to pay for hosting.
So to tell the average person that they can run a forum or a web site as a job - a reasonably paying job - is certainly and unquestionably nonsense. I think telling them that sad fact up front is doing them a great service. You should go into things with your eyes open, knowing what the odds are against you.
If you personally beat those odds, good for you. You're the 00.001% For the rest of the people out there, "I'll start a forum," is not a good business plan.