said by NG :
But I thought Bell sold the service based on the fact it's not a shared connection (like cable) so why would they have to throttle?
Normal large-scale networks aren't built to handle 100% end-point load routing capacity in everywhich direction. The only difference between cable and ADSL is the point at which the sharing and over-subscribing begins. With cable, it starts right on the coax and this makes the shared nature plain obvious. With ADSL, sharing begins at the DSLAM's ATM backplane. Beyond this point, both technologies become very similar.
The whole internet is an oversubscribed shared network that would not be able to handle every internet user simultaneously going at full speed.
Simply look at TSI: their traffic peaks are currently around 2.5Gbps. With an overall average of about 50GB/subscriber/month which is less than 1/4 of what is possible at 1Mbps, TSI would need over 20Gbps of total transit capacity to provide non-blocking full-speed for everybody assuming an average sync speed of 2.5Mbps. But for the time being, everybody east-side is happy with TSI's current 3xGbE links to Bell-land... modulo Bell's new wholesale throttling.