Spamming /tell to people does disconnect people if it over-floods them
make a macro like the following:
/tell AFK_PLAYER_NAME aaabbbbbcccc ( as much letters as possible)
/pause 0.01
/macro macro_name
spam this as often as you can. the afk guy will possibly loose connection, but you might too.
you can try this with more than one account at the same time for a better result
I did not find this guide/hack/exploit. I am simply just passing it along to the good people of l33tness. =D