They are breaking a lot of laws by doing this. There are plenty of regulated industries in healthcare and financial services using slack.
I can tolerate Slack and/or Salesforce at large building per-customer overlays on top of a generic LLM. Those at least can provide actual business value[ß], and give their AI teams something to experiment on. But feeding gazillion companies' internal (and workspace-joined!) chats to a global model? Hell no.
Unsurprisingly, we opted out a few hours ago.
ß: a smart, context-aware autocomplete for those who need to type a lot on their phones would not be a bad idea. The current generation of autocorrupt is obnoxious.