Aruba has just posted their most recent VRD (Validated Reference Design). In the past we've relied on VLAN pooling for large WLANs do to the issues with broadcast and multicast in large subnets. Optimization of these now allows WLANs with a single large VLAN/Subnet simplifying deployment.
"Rather than using conventional design with VLAN Pooling and multiple smaller subnets, we think that there is a better way to design WLAN today using 'Single VLAN with One Large Subnet' to serve all the wireless clients connecting to an SSID. This paper explains how we came to this conclusion."