LANs are now ubiquitous. Most broadband-connected homes have at least 4-port LAN switch in the modem, and in a modern office building a single room has 3-4 Ethernet sockets. Many new laptops have 1 Gbit/s Ethernet connections, and their wireless is up to 100-200Mbit/s with 802.11n.
Our solid view is that successfully engineering and maintaining a growing LAN needs measurements down to each individual port of the network. Client computers and wireless access points can now easily generate some 300-400Mbit/s traffic peaks, overloading the usual 1 or even 10 Gbit/s trunk connections in a flash. Most new LAN switches include sophisticated methods for prioritizing and throttling traffic, but these features are easily left unused if there are no measurements to back up the prioritization policy.
I hope that this enlightenment soon reaches 3G mobile networks too. But more about it later.