IANAL, but here is my thinking: The problem with personal phones is they are hard to audit. When a phone belongs to the corp, corp owns the phone, and "probably" can audit it as it wished.
In order to install my work Gmail account on my phone, I had to install a program on my personal phone that let admins wipe it remotely. This is not something that bothers me, because I expect to lose the phone almost anytime, so the contents on it are backed up continously on a system I control.
Whereas that bothered me so much I refused to put email on my phone and told my employer they needed to provide me with a phone if they wanted me to always be on email.
I'm already answering emails out of office hours which is for my employers benefit and they want to functionaly own my phone because of it?
