If you go to VMK Central Plaza and don't see any DIS'ers...
...it may be because you are in an alternate universe.
No really.
Each room in VMK can only hold a maximum of 15-20 people, and there have been up to 1,100 people logged in at once. So how do they do it? With different instances.
Each room in VMK has multiple instances -- the room looks identical, but each contains different sets of people. So, if you go to Central Plaza, and its empty, it might be because the instance where all the DIS'ers were hanging out was judged to be crowded enough, and VMK shunted you off into a new instance.
How do you control this? Under the Globe button, there is a checkbox for "advanced mode." If you activate it, whenever you use the globe menu to go to, for example, "Central Plaza," you will be presented with all the instances available named by compass points (like North-East, South, etc.) and a number of heart icons, which represent how crowded that instance is. Go to the most crowded ones to look for us.
Of course, if you have someone on your friends list, you can go directly to the instance they are in, without needing to check instance after instance.
Hope that helps more than it confuses.