Rogers prioritizing traffic

As a follow up to an item about Rogers blocking podcasts, Mark Evans called Rogers who said they were not blocking podcasts but rather providing priority to email and web traffic (Saunderslog).

While it does make sense for some IP services to be provided with higher priority than others, this could take us down a slipper slope. Who decides what traffic gets priority? Would all real time traffic get priority or would real time traffic from competitive services (non-Rogers VOIP or IP-TV applications) be left with low priority? For example, if web and email traffic are given a higher priority, everything else by default would get low priority.