You do not hear a lot about VLAN security anymore because the best practices have been adjusted to account for these kinds of vulnerabilities.
The way we used to configure VLANs had some security problems that needed to be addressed, these problems were researched and the best practices were revised to include things like: not using VLAN 1, using a black hole VLAN as the native VLAN on trunks, hard setting user ports to access, and so on. The fact of the matter is that if you are implementing these best practices, you are quite safe. The remaining ways that VLANs can be exploited generally require that the attacker have physical access to the switch, and if they have physical access you are already screwed.
Greg
