Wireless Guest Access

[roberticoles () gmail com]

Greetings,
Does anyone else see a problem with hosting multiple vlans on the same access point, one being guest access (open) and 
the other being company data (wpa2).
The installer claims that because it's using lwap to a wism controller in our dirty dmz, it's secure.  This comes from 
the same installer who claims non-broadcasting the ssid is a great security measure.
A username and password is requested via a splash screen from the wism controller when a web browser is opened and 
makes a request to the Internet.  However, they give the same id and password to a bunch of consultants and only change 
it every 30 days.
This same guest vlan access is wide open (no port blocking).  It does use a pat'ed address on the edge (IP address is 
from the same block from our ISP).
What about being blacklisted if something malicious occurs?
How about vlan hopping?
Other security risks?
Thank you in advance for any feedback provided.