said by Lazlow:That is just it, caps do not address congestion issues. A user could do all his downloading during off peak hours(download many times the cap) and NEVER contribute to congestion. Conversely a person could do all their downloading during peak hours (never going over cap) and cause a lot of congestion.
As far as costs; both transit costs and hardware costs are defined by Mbps of peak time use. Off peak downloading costs the ISPs absolutely nothing extra.
And if the heavy users were to start downloading during what is now off-peak hours... they then become peak hours.
You're correct that it's more a matter of peak use leading to congestion, but it would be difficult and confusing to have different caps for different times of day. The person downloading 400GB/month is likely doing it both during peak and non-peak hours.
The ideal scenario from a provider perspective would be to have hourly caps, but I doubt that would go over well with consumers.
And just to remind everyone- practically ALL bandwidth on the Internet is shared bandwidth. From your serving node to internodal trunks to the ISP trunks to host capacity- all shared. It's the reason broadband costs $40/month instead of $400/month.