Would this fall under wiretapping? Other IM services have blanket statements on monitoring all and any communication in their TOS, this just takes it to voice and video.
I guess what I was thinking of was something akin to Google AdWords, not the "they want to control the world" conspiracy theory edge.
Sorry, "wiretapping" was probably not a well chosen word.
Serving ads to unpaid users is a good example of something that people probably wouldn't find too creepy (not too different from seeing ads on gmail). The problem is that since MS controls the client software, it's not something that they would need to do at the supernode level. They could just run the voice recognition / keyword selection on the client and then request the appropriate ads.
Even if they were planning on some more wide-ranging thing with adverts than that, it's unclear why they'd need intercept the conversations at the supernode rather than at the client. They'd also have the problems that they don't have a credible display ad service to use this data for, and that they can't correlate the data from a logged in Skype user to some random web user who isn't logged in.
If we assume MS is taking control of the supernodes for some observation purpose, the observation needs to be something that can't be done on the client, or that would look suspicious when done by the client. E.g. storing all the voice streams for later analysis, or transmitting summaries of conversations between paid Skype users to some MS address.
I guess what I was thinking of was something akin to Google AdWords, not the "they want to control the world" conspiracy theory edge.