I should also note that most mushes use the default telnet port and don't use SSL.
Default telnet sends the packets from your PC (username, password, pages, TS scenes, etc) in cleartext through the default telnet port to the MU, making any information contained easily read by sniffing programs, spyware, etc. Even if you use a port other than default, telnet by itself is an insecure, cleartext protocol.
So unless a game is utilizing SSL connectivity (which encrypts the transmission rather than sending it in cleartext), you should also be aware that there is a risk when typing sensitive information sent to a mush on the client-side.
Like...if I weren't a musher and someone in my house was, I could theoretically set up a sniffer to monitor all incoming and outgoing traffic on TCP port 23 and just read what's getting sent through my router to any mush activity in my household.
tl;dr I highly suggest a mush culture migration to adopting SSL as standard.
ETA: This is in topic with the privacy talk the last few posts in this thread, as well as a suggestion as to how to take care of your players. Giving them access to SSL as an option treats them well.