There are legitimate arguments to be made concerning users' exploiting broadband resources beyond reasonable bounds, and this remains an item that is open for discussion and probably warrants some pricing adjustments, or redefining service offerings. Stepped micropayments come to mind, but there are other methods being explored, as well, including time of day, day of week, all of which were either tried before, or are actually being employed elsewhere in the world at this time. And similar dynamics surrounding slower speeds caused by congestion and increased latency will soon befall urban municipalities currently installing unrestricted wireless networks for the commons, as well.
However, when it comes to wireline broadband services offered by the incumbents, they will very likely leverage that same argument to thwart free VoIP services in order to restrict users from using alternatives to their own revenue-producing voice services, even where the latter offerings by the incumbents may also be VoIP, as well.
Truth be told, while VoIP works best over broadband facilities, it doesn't "consume" very much bandwidth at all.
Instead, the intermittent and burst nature of VoIP traffic merely demands that there be sufficient "availability" of bandwidth on an instantaneous basis to ensure that "headroom" exists to allow voice packets to flow unobstructed when VoIP packets DO occur. It would be wrong, in other words, to compare the sustained bandwidth "utilization" effects of movies and music files, in terms of gross file sizes, to that of VoIP.
In fact it is for this very purpose, i.e., to meet the demands of applications on an instantaneous basis, sustained to yet undefined time limits -- and it is this parameter (the treatment of sustained flows) for which an algorithm must take over, even if tier-ing is to occur -- that remain among the beneficial results of increasing bandwidth in the last mile, in the first place. For what other reasons would the cable and telco operators be striving to outdo one another by jacking up downloading and even uploading speeds in some instances every several months, otherwise? Except, of course, to benefit Madison Avenue, which seems never to be able to sell enough cross-modal bashing to the incumbents for the placement of ads on TV and the radio. And, for what? To be told that you can have the privilege of paying for the bandwidth, but you can't use it?
One could suggest that the Incumbents' light more lambdas over their fibers in the transport networks that feed those last mile access networks, and start taking advantage of the alleged bandwidth glut that is said to still exist, and stop whining over red herrings like VoIP, which, admittedly, does serve to draw revenues away from the incumbents, but at the same time do not consume all that much bandwidth. For what it's worth ...