I will add this, however... there's perhaps a mechanism we can use to invalidate the favicon using a cache buster but that would then essentially mean it is downloaded re-cached on every page load, which doesn't seem ideal.
If it's something you wish to switch off on your own forums, you can. In the Admin CP search for "Display visitor count".
The favicon is cached in Firefox and if you happen to make a bookmark while the red dot is showing then it's very difficult to remove the favicon and it will always show the red dot. In order to remove it you have to install a Firefox add-on called SQLite and delete the favicon from the database.
I think a better solution to this issue would be to make the default selection be "Count in title" so that this problem does not occur. If you take a look at other major sites like Facebook and Twitter, they don't mess with the icon, I suspect for this reason.