Spectrum online features a well-written article about the seven myths about VoIP: "Seven Myths about Voice over IP". It picks up on some common misperceptions about VoIP and explains in good detail the principal nuts and bolts of VoIP. The seven myths are:
1. VoIP is free.
2. The only difference between VoIP and regular telephony is the price.
3. Quality of service isn't an issue nowadays, because there is plenty of bandwidth in the network.
4. VoIP can't replace regular telephony, because it still can't guarantee quality of service.
5. VoIP is just another data application.
6. VoIP isn't secure.
7. A phone is a phone is a phone.
These "myths" are certainly not new to industry insiders, but I recommend reading it, because it depicts in very understandable language the concept of VoIP and is getting the point across, something e.g. I have sometimes struggled to do when explaining it to non-insiders. Must-read for newcomers.