I guess that's what they are hoping for.
I used to go to the autosport F1 forums all the time to talk about racing.
Now only once every few months, if that... Why?
They added a persistent bottom banner ad that you had to click off with every new page. Just too annoying for words.
And I still get the pop-up and bottom banner ad on every new page here.
So yeah, my engagement will wane.
Not like I have a huge post count compared to some, so I guess they'll chalk it up to no big loss if they get sufficient members signing up to avoid the annoying ads.