The 'C++' keyword however, already narrows the target down to the 0.2% of the population, i.e. C++ devs. making it 500x more effective than a non-targeted ad.
If only 10% of those typing C++ would ever be interested in a course, then those are not bad numbers.
More nuanced: at the 'non-targeted' threshold the ad would not make sense at all, total inefficiency. At the targeted threshold of being able to target at least C++ devs, the ad probably starts to work.
That is the difference between a viable business and not
That means engagement, value creation, sales, C++ developers trained and ready for the market. This is extremely good for society. We definitely want aspiring C++ devs hooked up with quality courses.
This anecdote very tangibly demonstrates the effectiveness of targeting for individual companies ... but it also points to the market efficiency that comes along with good advertising.
If you have a startup, and you can't reach any of your audience, you're dead. This notion of 'word of mouth' is ridiculous as a business plan, it's exceedingly rare, and usually it's not that anyhow in reality - it's usually a form of effective social marketing by the early movers. Clubhouse for example is being helped by the 'celebrity' of the VCs behind it - they don't have mass market following, but a very avid following in a certain niche that will come onto the platform. I'm noticing a lot of Marc Andreseen on Clubhouse, too much for a busy VC, but not too much for someone who's hyping his own investment and bringing in a lot of viewers, helping out a lot of panels.
The essential nature of basic targeting is not controversial, it's quite obvious at least at the most crude level.