This is probably like reopening bug 1040956 for Horizon... I'm not sure everything was addressed within it though, feel free to close if my reading is wrong.
1. If Quantum is enabled, at the moment we're still getting the floating IP quota from Nova, thus displaying wrong information in the system panel.
2. I believe this also means we're updating the wrong service (or at least it has no effect) when an admin updates the Floating IP quota using the Project panel, which is misleading. (This is similar to bug 1095876 for Cinder.)
3. Additionally, because we use that same quota information to sometimes disable the Allocate IP button (will be more of a problem after bug 1109098 is fixed), the user could be prevented from allocating new floating IPs when they are actually allowed to have more. The bar chart on that screen also displays incorrect information.
1. Update /etc/quantum/quantum.conf [QUOTAS] section with "quota_floatingip = 3" (from http://docs.openstack.org/trunk/openstack-network/admin/content/cfg_quotas_common.html) and restart the quantum services
2. Go to the system info quota tab: Floating IP still shows as 10
3. Go to a project's Access and security tab and try to assign 4 IPs: the 4th one will fail with "Error: Unable to allocate Floating IP." Also the Allocate IP button isn't disabled and the bar chart wrongly indicates there are 7 IPs available.
Reproduced on a recent devstack.