Traditional LAN design suggests limiting subnet sizes with a /24 being one of the more commonly seen subnet sizes per VLAN. This is typically to limit the number of broadcasts & un-bounded multicasts.
I imagine these suggestions came from the days were 10Mb/s NICs the the most common and workstations / server CPUs were much slower (not to mention NIC hardware processing capabilities themselves).
In a modern network with 100Mbps NICs, fast CPUs and even things like checksum offloading to the NIC, in addition to the percentage of traffic per host that is made up of broadcasts & multicasts, I can't think why there would be any problems with /23, /22 and even /21 subnets.
Running a wireshark on my workstation (on a /24 subnet, with about half of those hosts active) I see ~ 24KB of traffic in a one minute period (equaling about 0.5KB/s). If we extrapolate this from the ~128 hosts up to say a /22 subnet, we get around 5KB/s of additional traffic for each workstation to process. I do not see this as much of an issue in a modern network with modern workstations & servers which should have no problem with 100Mb/s or 1000Mb/s of network traffic. In fact, even on an old network, this is a negligible amount of traffic.
Additionally, the only useful non-network (CDP, HSRP, STP) traffic seen in my Wireshark was ARP, DHCP & NetBIOS. If this network management traffic was eliminating from the user VLAN, the figures listed above would be even lower.
Can anyone point me to some modern network design requirements that do not flippantly suggest broadcasts as the reason for limiting subnet size or weigh in on anything I may have missed.