I used to run an active, unlimited TOR exit node on my office PC during non-work hours, that is until for some unknown reason our office had our Skype account blocked - I called Skype, my network provider, everyone trying to figure why we couldn't access Skype at all from any of the computers on our office network (we have a fixed IP which could have added to the problem).
I read some threads on the Skype forums that this has happened to several people - apparently once Microsoft integrated Skype over the last year, anyone running an Exit Node was blacklisted. Note that we got any kind of notification, just a banned IP, they would not even confirm we were banned. I shut down my Exit Node and about 2 weeks later Skype returned. Not exactly what I call a positive treatment for a so called "good application."