[rtpg]

>For all you know they could be doing stock trades based on all the insider info they can glean from their chat traffic as their business model.

From the Slack TOS:

>Your acceptance of this TOS gives us the permission to do so and grants us any such rights necessary to provide the service to you, only for the purpose of providing the service (and for no other purpose).

They _could_ be breaking the TOS (and thus the contract between you and the them), but I doubt it.