It's like facebook in that the employees had a guarantee of privacy (insofar as most private communication is private; obviously the recipient can expose the message, or someone can coerce you to login to your account). Some people are waving this away with, "oh, probably the employee signed some contract saying that it wasn't private" but even if that's often true it's of course sometimes not true. Certainly I've never signed a contract with that kind of clause, but I've generally worked for small companies.

I suppose there's nothing preventing a company from using facebook as a corporate communication medium. That'd of course not a good idea since they don't have access to some of what goes on at facebook. The same thing was true for slack. Some companies used slack without considering that the data wasn't really under their control, which was perhaps not a good idea. This change is akin to facebook recognizing that blunder, and "fixing" it by making DMs between employees available to their employer.

> It's like facebook in that the employees had a guarantee of privacy (insofar as most private communication is private;

Nope. You could be compelled to show your DMs on a work system.

There is no such thing as privacy on a work system.

"Wait a month" if you do that, then slack just cost you thousands of dollars. How mad I'd be at slack would be proportional to how may thousands of dollars they just cost me.

Such is the cost of constant surveillance? You need to weigh the pros and cons in any situation. If you don't think that you saw such a DM is relevant, then consult your lawyer and fire them. If you feel it best to wait, you wait.

Also, how is this different from Email?