I'm sure I am not alone in finding this very irritating. Even more irritating is the way it cuts down the window size. I set it to maximised and expect it to remain that way, not get hijacked by an add.
I'm NOT saying that it's FALSE information, simply that it's creative advertising. Obviously the number registered is correct, BUT, how many are still ACTIVE, i.e. come back after their query has been answered?
I don't have the answer to that, but I do know that many members/Users of the forum do come back time after time.
Many don't post on each visit, but come to read and find answers that way. I do know of several members that have not posted for some months, six or seven months but are still active in the sense that they still use the forum on a weekly basis, if not each day.
I may have misunderstood your post, but it does come over in print more as a criticism on the Forum than support of it, and I don't think you meant it to be that way.