said by NetAdmin :

First and foremost, you are correct in the assertion that providers can never have 100% bandwidth available, 100% of the time. Those of us who work in the industry work our hardest to ensure that we can get as close to that as possible without breaking your or our bank.

However, you seem to overestimate the ability of QoS and underestimate its abilities to have undesirable effects. I went and found the conversation you had with the moderator many moons ago. Yes, QoS is very useful in helping out time sensitive applications, but it can also create issues, as was hashed out in your conversation with the moderator. The moderator was correct in the statement that prioritizing classes of traffic has an effect on other classes of traffic and it can be negative.

There are other limitations to QoS, which I think were touched on in that conversation you had with the moderator. If QoS is not maintained from your system to the target host, its usefulness is severely limited. Here's an example - All providers love peering points, but peering points are oft congested and there is no QoS at them. So a VoIP call that maintains a good flow in the first mile due to QoS can be totally decimated at a peering hand off. And then there is no guarantee that your ISP's transit provider or peer will even respect the QoS assigned to your packet anymore.

If you and others are going to advocate QoS, it needs to be advocated across the board, on up to transit providers. However, before that position is taken, people need to understand what type of impact that would have...