said by a333 :

DOSCIS 2 shares the 50 megs among like 50 users, so comcast cant use it to offer those speeds to each and every sub. Now, hopefully, with channel bonding and the rest of it, DOSCIS 3.0 should be able to make those speeds possible.

said by alchav :

I agree with a333, Cable Companies and Telco's are laid out differently. Cable Companies work on a sharing Network, while Telco's Network starts at the Central Office. DOSCIS 3.0 or Fiber through a Cable Company will still have limitations. Like I said Verizon FiOS is the clear winner anyway you look at it.

said by Heyya :

Thats incorrect. Fios uses two data lightwaves upstream and downstream and both are up to 622mbps on BPON. Plus its using TDM so its not actually shared like cable.

said by espaeth :

FiOS uses TDMA on the upstream as well to solve the "multiple speaker" problem in the same way as cable. Based on my understanding of FiOS, each neighborhood distribution would share 1 port on the head-end. The downstream light path is split to 32 homes with the head-end being the only speaker so there's no chance of transmit collision. Each of the 32 homes off the distribution node sees the same downstream data feed just like cable. On the upstream each home is fed into an optical combiner to go back to a common upstream node port. The reason you are limited to 155mbps upstream is because of the TDMA timing overhead to ensure that upstream data transmissions are handled in a controlled fashion and 2 ONTs don't transmit at the same time.

The biggest difference is network scaling; Verizon needs one head-end port per 32 homes, whereas Comcast can go as wide as 1 head-end port per 1000 homes in some cases.