802.11s Mesh scalability?

[narmenia]

I read this earlier

Setting up 802.11s for meshed "dumb APs"

The simplest setup is to bridge both the mesh interface and the wifi AP into the lan network at each dumb AP. The dumb APs would not run a DHCP server, all DHCP requests are handled by the main router. This kind of setup has some issues with scaleability and security, but it is the simplest way to get started and is entirely workable for having a few nodes around a house that are not accessible by the public. It works much like having the APs connected to the main router by a network of Ether…

This kind of setup has some issues with scaleability

what is the issue with scalability?