There seem to be two issues here:

• A cosmetic issue - people look like they are here when they are not.
• A load issue - people leaving their chat client open when they are not around.

But in either case, the reality is that user education and finger pointing is only ever going to go so far in fixing the issues. There will always be people not logging out either out of laziness, forgetfulness, being distracted, etc..

Step 1 think about both issues and decide how important they really are. Step 2 if either of those issues turn out to actually be important, then find a way to solve the issues on the server side so it doesn't matter if people log out or not.

Personally, I've hacked my version of getchat.pl from the default distro so that it alarms out if I leave it alone for too long. It probably also wouldn't be too hard for somebody to do that with the framechat client also.