The other risk that mobile devices create is that they could get infected when off the network and then spread that malware around when it reattaches to the business network. Typically, user connections don't need to connect by going through a next-generation firewall or an IPS system, so the only way to understand if the device is causing harm is to look at the flow information going to and from the device and quarantine it on anything anomalous.
I'm certainly not saying that businesses should ditch the BYOD efforts or stop supporting mobile devices. That would be business suicide, as workers would revolt. The important thing to understand is that an increase in mobile devices increases the chances of a breach, to the point where all companies should accept the fact that it's probably going to happen. There needs to be a focus on understanding what to do when the breach occurs and how to mitigate against it before serious damage is done.
Sign up for CIO Asia eNewsletters.