Is VoIP too secure?
It's hard to imagine, but roughly 10 years ago as VoIP was being rolled out corporate networkers were quite concerned about the security of VoIP. As we faced a move from voice going over a traditional (and, by the way, unencrypted) network, there was concern that VoIP would be much too easy to eavesdrop on - especially if it traversed the Internet.
We'll leave the question of whether "legal intercepts" as a political and civil liberty question. Indeed, virtually any "good" technology can also have a dark side. Nevertheless, "wiretaps" have been a part of voice communications essentially forever. Sometimes for the good of all. Sometimes not.
And "tapping" a traditional voice call, whether in analog or digital (PCM) format is trivial. Additionally, as discussed in an excellent interview, "Web Wiretaps Raise Security, Privacy Concerns" on All Things Considered, as cellular technology was rolled out, there were provisions made for "lawful intercept."
