Banning Meebo sites in BorderManager can be a bit of a pain.
Here is a quick and easy way to block them in BorderManager using two rules.
New Rule > Action Deny > URL > Destination > Specified > Specify URL > http://*.meebo.com/*
New Rule > Action Deny > Application Proxy > Access Details > Proxy HTTP > Origin Server Port: 443 (leave "to" field blank)
Destination > Specified > DNS Hostname > *.meebo.com > Add > OK
Disclaimer: As with everything else at Cool Solutions, this content is definitely not supported by Novell (so don't even think of calling Support if you try something and it blows up).
It was contributed by a community member and is published "as is." It seems to have worked for at least one person, and might work for you. But please be sure to test, test, test before you do anything drastic with it.