The ACCC is concerned that by being connected to the NBN in a similar fashion, ISPs may get sneaky on speeds (who'd have thunk it?). So the commission says it will take action against providers breaking its key principle: “Headline claims must represent attainable speeds”.
Given that NBN Co will offer ISPs a variety of wholesale options (enabling products as slow as current generation ADSL all the way to the high-end), the ACCC has this to say:
ISPs (and not NBN Co) are responsible for determining what inputs are necessary to ensure that real-world NBN service performance aligns with marketing claims and resulting consumer expectations. Specifically, if ISPs under-provision their CVC (basically, their NBN virtual circuit) and/or backhaul transmission capacity, end-users will often not experience data transfer rates that match their purchased plan’s headline rate.
Essentially, high-end services will need contention ratios that prevent shitty performance at peak times, and budget ISPs will still need enough capacity to actually deliver the speeds they advertise.
ISPs are likely to want to market this performance advantage by referring to the maximum data transfer rates on the plans offered to consumers—describing plans as ‘100/40 Mbps’, ‘50/20 Mbps’ or ‘25/5 Mbps’ for example.
However, claims about the data transfer rate applicable to a given service are likely to be misleading unless that rate is attainable in practice by end-users…
Bottom line: ISPs will be more responsible for the real-world data rates experienced by end-users, subject to obvious user-controlled stuff like BitTorrent sprees and securing your Wi-Fi network. [ACCC (PDF) via ITNews]