It actually doesn't matter how many users there are on an individual board
- it's the amount of activity on the server itself. If the server receives xxx requests all in the same instant, then it can't handle more than a certain number. In that case, it rejects the ones it can't handle and gives the users that message.
Though I haven't heard directly from BbBoy today, the recent significant drop in those messages led me to believe that he had made some sort of adjustment - though what that was, I don't know yet - maybe he didn't even make an adjustment.
As I've mentioned elsewhere, there is still one element at play in all this and that is the deleted free boards - anyone trying to access them will initiate a server request each time they do so and this being a holiday weekend, user activity is high.
For the moment, it seems things are pretty much improved, with just the odd message, so we'll just keep our fingers crossed that the situation doesn't deteriorate again.