Limit online users

Is there a way to limit the number of online users to say 10, 20 or to any limit you want to set

For people on shared hosting plans this might be a useful feature to have

Do you mean number of people on home page ?

I mean the number of people logged into the site at the same time.

If I can limit the number of people logged in to the site using resources like uploading video etc I can then limit to an extent CPU usage Mysql hits and so keep it so that you cannot get 70 people in a chat room at the same time.

Hope this helps to explain it a bit better