Your backbone should be larger than the pipes that connect to it. If your network is entirely 100BaseT, a 100BaseT connection is probably not going to be big enough for the backbone. Use of ATM or Gigabit Ethernet will help you solve bottleneck problems along the company backbone. Protocol shaping is becoming more and more popular as a way of controlling bandwidth use within organizations. Protocol shapers are hardware devices that allocate network resources according to specific protocols.
More bandwidth is always better than less bandwidth.
100BaseT appliances have more features and more capabilities than 10BaseT appliances. In 100BaseT networks, each client occupies its own collision plane, allowing it to take full advantage of the bandwidth available. Many 100BaseT switches also support some Level III capabilities, including the ability to manage IGMP groups. 100BaseT Hub and switched networks can also be used for streaming. This hybrid network can support streaming if it is not over utilized and deploys 100BaseT hubs.