By going on there site they can do most things without having to ask for permission.

Also i dont think they would store your IP. It should like some kind of browser error. Your browser must have saved the cookie and the radio panel just sent it to everyone who was online according to the panel.

Also im not sure about this but on a forum you can go online for 2 minutes but appear on the whos online box for a certain amount of time (set in admincp). So maybe a site like clubhabbo is the same?