Quote by patokl
What remains unclear to me, is how members, who choose to be invisible when online, are counted in those statistics. If they're not, actual numbers could be a lot higher.
Members choosing to be invisible has nothing whatsoever to do with it. Go to your forum homepage, scroll down to near the bottom where it says "active users" and it says something like this: 2,373 active users - 194 members, 2,179 guests.
That tells you how many active users there are currently on the site, and how many of those users are logged in and how many are visiting as guests. Members being invisible doesn't have any influence on those numbers.
Once that 194 members drops even lower and reaches 10 or 20 people, what do you think is going to happen to this site?