Funny most of the time people blame the tunnels for getting hacked.  My opinion is that your were already infected.

Packet "sniffing" is a well known online hazard and tool for hacking, and due to that most programs that involve sending sensitive information outside the computer have built in some sort of encryption system to encrypt that data, just the same way your browser uses SSL for some websites. So this means that the data travels encrypted and only WoW login server has the key for it when you use a SSH Tunnel, providing it was setup correctly..

Although, like with everything online, caution is obviously necessary, nobody ( maybe TM and your gaming addiction )force you to use and/or purchase a tunnel service.

My team is constantly keeping an eye out for unusual activities going on the servers ...

Be wary and alert on programs Tunnel service ask you to install. If you do need to get, ie PUTTY or Proxifier or whatnots, get it from the original site.
Like I tell my users, if you download the registry editing putty server configs for the tunnel service, open it up in notepad and take a look before you install .

But one thing to think about, you think i would ruin my name and business over hacking WoW players? Too much work ! I rather sit back, buy new tunnels, have my team administer and i sit back and relax ...