It's true. Some companies disallow it altogether. Everywhere else, it's just a bad idea (he says, typing this comment on his work laptop).
However, the answer is not to bring your personal equipment onto the corporate network. Which sucks because if you need to get something taken care of between 8 and 5, how are you going to manage that? Your options are limited if you don't have a guest network at work.
Yup. (As I type this on my work computer too). It sucks. The limited options are go someplace over lunch to get it done, take PTO if your employer is inflexible, or find a new employer.
Your personal, private, and confidential dealings while using employer provided equipment, networks, and time are anything but those things.
However, the answer is not to bring your personal equipment onto the corporate network. Which sucks because if you need to get something taken care of between 8 and 5, how are you going to manage that? Your options are limited if you don't have a guest network at work.