Personally there is a difference between logging into Slack on my phone and logging into email (which requires me to enroll into the MDM). I do the former on my personal cell phone, but I would never do the latter. There are many mistakes the company can make (like wiping my personal phone after resigning from the company) to make me regret that decision. But installing Slack is different, I can shut off the notifications and it is oftentimes convenient for me to have the access there if I need it.

Proverb from HPMOR: It's not paranoia if they really are out to get you.

I used to be very strict but I kind of had to give in on the work email because it was so inconvenient. From what I’ve read on iOS this gives them fairly limited access to my activities. Well, hopefully true.

If you're ever caught up in discovery or a lawsuit, you'll realize why many of us believe in multi-device and firewall policies.

That's not what people are talking about, they're talking about fully merging your personal and work accounts for things like iphoto, email, etc like Apple is talking about above.