How common are wide open SIP gateways?

[Drew Weaver <drew.weaver () thenap com>]

Heya,

        Has anyone done any research or have any anecdotal numbers related to how common it is to have a SIP gateway 
sitting out on the Internet with no ACL or authentication? Recently we have noticed a couple of instances where we get 
abuse complaints from companies who claim that one of our hosting clients 'stole SIP service' from them. This reminds 
me somewhat of the 'SMTP open relay' days. We obviously take action and shut the offending user down but I can't help 
but wonder how common this practice is. Usually I just ask the company why their system allows anyone to use their SIP 
gateway and they usually say something like "We can't predict what IP our users will come in from... etc"

I am just wondering if anyone else has noticed this trend.

-Drew