Network security: public service

You know the cover pages full of adverts that many free internet services ( hotels, restaurants, etc..) have? What if they included a little embedded application that showed a stream of all of the clear text passwords being transmitted over that network as you connected? Obviously, you would not want to attach the login username to it, or make it really useful-- just make people aware that there are many applications out there that use cleartext passwords and if you are on an unsecured network, this puts you at risk. I saw a related app on the showfloor at last years SC09 and it raised a lot of eyebrows, even amongst the geeks who attend a supercomputer conference. What do you think the results of this would be in the general public??