[waza]

first of all: 3 extra queries per page is a lot dude. However, I guess you could use a cronjob once a minute to cache the results.

But still that would use a lot of extra memory/size per page.

Then there is the fact that it's just not interesting information.
The first column shows all the online users in a small list, if there are more than 500 users online, who will go through that list??

The second and third column may be a reason for people to spam with a lot of short messages and stupid threads.